I believe what the parts guy is asking about is the number of pinion bearings. Some have 2, some 3. You would probably have to look at the axle ID then have the dealer run it to be sure which you have.
They are not refering to the bearings or the (drive) pinion gear in this case but the pin(s) aka pinion that the spider-gears ride on. The 2-pinion design's differential case is a one-piece design and has one large pin that slides through a hole on each side of the case and that has a spider gear on each end of the pin for a total of 2 spider gears. The three pinion setup has a 2-piece diff case and 3 pins that meet in a center "holder" and it has a spider gear on each of the three pins for a total of 3 spider gears. Strange design but the 3-pinion is 50% stronger than the 2 pinion. (For the same price)
When I swapped my 3.73's for 4.30's, the parts guy asked me the same things:
Is is a 2 or 3 pinion? (17 pinions, the more the merrier.)
Is it a 5.4L Diesel, 6.8L Diesel, 7.3L gasser or 6.0L gasser? (1.3L 3-cylinder Propane)
Is the truck white or red? (In Texas, you gotta be kidding, white of course.)
Vinyl seats or cloth? (My trucks has no seats.)
Pine-scented or strawberry-scented dangly that stinks up the cab? (Nope, Cocconut)
Is if front wheel drive or rear wheel drive? (Neither, it's 3-blade propeller-driven.)
Leather wrapped steering wheel or vinyl? (Nope, bacon wrapped.)
When you lick the exhaust manifold, does it taste like chocolate or vanilla? (Wife doesn't allow extra-curricular licking, sorry.)
They also told me that my axle doesn't exist. I have a 425F but they said Ford only made a 425B, and there are no 425F in existance. I went outside to check, and sure enough, my rear axle isn't a real axle at all but just a hollogram of one and is depicted with dotted lines. It is a gaseous entity, not a real object.
Anyway, I cast their BS aside and I picked a gear set at random and got a part for a 2004 3-pinion V10 axle since there is no 4.30's available for 5.4L's and my truck has (had) a 2-pinion diff case, being a 2003 5.4L. Go to any after-market ring and pinion manufacturer and no one even bothers with making a distinction between the two and three pinion designs. It's still a 10.5" diameter gear and still has a differential case of the same diameter with the same number of ring gear bolts, spacing, and size and with no carrier break. Case in point, the similar 10.25" axle only came in a 2-pinion flavor and you can install any 10.25" gear set on a 10.5" axle. (Provided you use the larger drive pinion bearings, which has nothing to do with the spider-gear pinion.) Same same.
I'm not sure about Ex's but on SD's, the 1999-2004 5.4L's and reg cab V10's have the 2-pinion case, the 1999-2004 V10 ext-cab and crew cabs and all diesels have the 3-pinion type. 2005-2006 5.4L's have 2-pinion, all 2005-2006 6.8L and 6.0L diesels have a 3-pinion. Probably, the 5.4L Ex's have a 2-pinion, while the V10 and diesel Ex's have a 3-pinion.
Put in a Detroit and you'll have a 4-pinion setup with 4 spider gears and a cross-arrangement pinion pins, even better. Either case (pun please) , it does not affect what part number 10.5" ring will fit on the case.
I went with the Ford/Visteon 4.30 gears. I was told by several shops that given the choice, they would pick the Ford gears as they are of better quality than any after-market parts. None of the shops I called sold the Ford parts so I'm pretty sure they were being honest. I didn't want to risk having a noisy gear set due to poor machining. (Real tomato ketchup Eddie? Nothing but the best!)
I also put in a Detroit No-Spin locker. The stock limited slip worked great in my truck, unlike all the people here who complain about it, but when one of the rear wheels was off the ground, it was very difficult to get the truck moving again being I don't have a 3-wheel drive. With the Detroit, that isn't an issue, it'll move, period. Plus the power slides are ridiculous now. After a few thousand miles, most of the clunking and roughness associated with automatic lockers went away. I guess it needs a good break-in too. An ARB air-locker might have been better since they are easier on the drivetrain. I haven't noticed any extra tire wear either. (Compared to the limited slip.)
Be prepared for some pretty good acceleration with the 4.30's. I swear this is true, but I smoked some kid in a 95 Honda Prelude from a dead stop 3 weeks ago. He thought I wanted to race because I let my truck roll back. He didn't realize that at my age, it's not that I want to race, it's just that I am too senile to remember to step on the brakes when my transmission is in neutral. This high-school punk was revving that thing up and letting it roll back too, while giving me "the look" but somehow, he only succeeded in achieving lameness since he had an automatic. It was "pants", as they say. I did a 3-5-6 shift and he got "owned" by a damned 5.4L F250! A farm truck! Not even a real man's truck or anything. (Not a diesel) He had a fart can exhaust on his car so I heard him at full open throttle the whole time, but the noise kept getting lower and lower... He should be ashamed of himself.
But I digress, the gear set part number I got was 3C3Z-4209-CA. That part number was for a 2004 F250, I'm not sure what year your Ex is. (1978 I think?) They probably have some updated part numbers for later year trucks.
They were pretty hard to find and also expensive:$400!!! I think it is because I got them from a Ford parts warehouse. BFR250SD said you could get them cheaper from West Coast Differential or Randy's.
You didn't say no by walking away while I was posting, didn't say no by closing your web browser, you didn't say no by turning off your computer. Now, will you open your heart (and wallet) and say YES to a Ford/Visteon 10.5" 4.30 gear set? For only $400, you can give your Excursion the necessities of life while providing hope for the future. Call the number on your screen now, don't turn away from the opportunity of owning a needy and underpriviledged 10.5" gear set. Little 3C3Z-4209-CA needs your care and support (and lubrication), call now.
You will receive a picture of your "sponsored" gear set with each $400 donations: