Building a 92' F-150 with a 93 built Cobra 5.0 with built E4OD. I am getting close to getting this truck on the road. I want it setup to run from a dig. That said and my old school ways, I am thinking 4.10 posi set up. I can always use tire size to adjust drivablity. With the OD, I am thinking it should be able to cruise at 75 mph but prolly not much more. Thoughts?

 

4.56 will help out the 302 and with overdrive 75 mph is no problem at all.
The only slight issue is when your pulling a hill at 75 when the tranny drops out of OD. The rpms will jump up to about 3300 and that will get old after a while.

4.10 would work too, but you are no where near topping out speed wise with them and a downshift out of OD would be a bit more comfortable.

What is run from a dig?

 

Run from a dig, is racing from a dead stop.... Drag racing in other words.
Ok so is this a 2wd truck, 4wd?
How big are the tires?
What is the level of "built" cobra 5.0?
What cam is in the engine? If it has a awesome rumpity cam you may not be happy with it no matter how much gear you put in it. Unless you have some tuning done and go to mass air.
What is your end game with the truck?

 

If you want a naturally aspirated 5.0 to get a 4000lbs truck moving, I'd go with a least a 4.56 gear. Reg street tires? Traction will be a problem.

 

The trans won't drop out of OD pulling a hill with 4.56 gears, the truck won't even lose any speed.

 

Sure it does. I have that exact combo and it does just that.
But it does take something like a mountain pass for it to become much of an annoyance.
So you either slow down or live with it.

 

You have 300hp 5.0 with E4OD/4.56 in a 2wd reg cab pickup with 29-30" tires?

 

I don't see where OP stated 2wd reg cab or 29-30" tires.... but you are correct , that doesn't exactly describe mine

Even with your assumptions, I still wouldn't be so sure about that. And that doesn't even account on if the owner opted to manually lock out OD for any various number of reasons.
Maybe my definition of hills is different than yours. Throw in a stiff head wind and it becomes amplified.

Nonetheless, and the point I was trying to make before, 4.56 is quite doable at freeway speeds, even with the OD off, just slightly annoying comparatively, hill or no hill.

 

And you are correct he didn't explicitly state that, so for the sake of comparing apples to apples what is your exact combo?

My experience with a similar combo.. 4.6/4R70w/4.10 gears with 31" tires is that it will climb a pretty good grade without losing speed or unlocking the TC at 70+ mph, steeper hills do make it downshift but it still manages to maintain speed unless the hill is crazy steep. And that is pushing a 6000lb full size van around.

If the OP has a relatively light combo something like Briansshop showed with a healthy 5.0 under the hood I just can't see performing worse than my van.

 

I'm still interested in his parts list for the built cobra 5.0. If its anything close to say, b303 with gt40 y heads... it will need at least 4.56s.

 

Or loaded with some kind of payload...

Kinda what I was saying.... Not sure why you decided to jump all over it.

 

Old age?
To many beers?
Real deal is what the OP wants. And how the OPs rig is setup.

 

I'd agree. It sounds like the OP is talking about a 2wd truck,so prob less than a 30" tire,most likely a 28".

Tire diameter?

 

The truck is a 92' f-150 extended cab, 2wd. The motor is 93' Cobra with GT 40 heads and pushing right at 400 hp according to the dyno pull I saw when the drive train was in a 80' model Mustang Coupe. The car was damn fast for the short period of time we drove it, maybe 600 miles before it was totaled I can find more details out on the motor build, my buddy is the who actually built it. I bought it for my son then a day after Hurricane Harvey hit, he hydroplaned the Mustang in the wet weather, totaled the car. I came across this clean F-150 for cheap with the intent to swap. Tires are currently stock but that will change once the gear selection is made. It will be run on the street and strip and will see its fair share of drag racing. We live in south Texas, flat land so no Mountains or passes close by. The truck is back at my buddies house currently waiting for him the finish the tune, hopefully it will be on the road in a week or so.
Thanks for all the input/advice, please keep the suggestions coming. I do like the idea of 4.56's , so what size tires would you suggest? I would be guessing 28-30" but its been so long since I had a hot rod, everything is purely a guess for me. Our wheel and tires choice is completely open at this point. I know it will not be as fast the Mustang by a long shot but it will be fun and more practical for our use.

 

Was it a carb setup or was it fuel injected. Really need to get the cam info from the builder. It is probably not Speed Density compatible so you may have to do a MAF swap for the truck.
And since you said you saw the dyno sheet at 400 hp. I'd wager low end tq is way down. I wouldn't put anything less than 4.56s in it.
And as for more practical, it may not be. The truck computer rev limiter will most likely kick in before peak horsepower is made, and it may actually be weaker as a truck because of the rpm range the cam makes its power in.
Also without a tune you will, depending where this engine makes power. You will have to manually shift the trans. Because the computer will shift at the factory programmed rpm, it may shift a 1000 rpm before the engine wants it to.