Bear with me this is a long story about my '65 F250...
Years ago I upgraded my front brakes with a dual piston caliper setup from a '76 Crewcab, everything went great, worked fine. A few months went by and I decided to upgrade to a power booster and M/C, which I got from a '70 4WD F150 I think. Just recently I replaced my rear-end with one from an '81, and that worked well too.
Here's the delemma...
I would like to make sure my components match for the system I have, and I think I pretty much have all the info with one exception. Do I have a rear-end from a truck with a GVW rating of over 8,500 or not, and the same question applies to the front brakes that I got from the Crewcab. This makes a big differance when you are talking about master cylinders, power boosters, and proportioning valves!
I do know the '81 rear-end is a Dana 61 and has 12 x 3" brake drums with 9/16 - 18 left-handed lug nuts on the left side(right-handed on the right)...it seems pretty heavy-duty, so it could be. The fronts don't seem as serious relatively speaking and the lug nuts are 1/2 - 20 all right handed, but the fact that this was a Crewcab may make it so, the springs under it were way stiff and would not work for my truck, I used the '65 originals and some spacers...worked just fine.
I am not running a prop valve now and do not have any wheel lockup issues out back, but I also have to apply more pedal effort overall since the rear-end upgrade....that's what has me thinking.
I hope it's under the 8,500 GVW for both, because the fronts are the same basic brakes from the '76 to the '81 and I would go an all '81 system(MC, booster, prop valve) then. If I have a mixed bag(under in front, over in rear), then I will either live with it as it is, or look to further upgrade the front to an all over 8,500 GVW setup.

This is a damn good reason to use all the parts from the same donor truck, but the cards didn't play out that way for me! All-in-all, it's still waaaay better than the stock drums!
Thoughts?

 

I haven't really messed with the 1980+ brakes but if you want your front lug nuts to match your rear axle, just get some SRW rotors off a 76-79 F-350. They have the 9/16" studs and just bolt right on since your using the 6900-10000 GVW spindles.

I do know your setup is pretty much identical to the 76-79 F-350's. 12 9/16" front rotors with dual piston calipers and 12x3" rear drums. I would just use the dual diaphragm booster/master cylinder and proportioning valve off a F-350.

P.S: My truck is messed up more than yours. 51 Mercury 1 ton body on a 78 F-250 Supercab frame, 68 F-350 front hubs, 74 F-350 rear axle, 7" dual diaphram booster, Ford 4 wheel disc master cylinder, 84 302 with 87 EFI and 92 AOD tranny.

 

How are you so sure that I have "6900-10000 GVW (front) spindles"? But you have partially answered my question, thank you. If there's no differance in the diameter of the rotor(which there isn't, mine are 12 9/16), and the calipers are the same, (which they are) then I can assume that the rear-end is the heavy duty unit and could go with all 8,500 GVW components? That would be sweet, then all I need is the M/C and booster from the F-350!

 

If you have dual piston calipers then you have the 6900-10000 GVW front spindles (Used on HD F-250 and F-350 trucks). Dual piston calipers won't fit the single piston caliper spindles (F-100/150/LD F-250).

Yes, just go with the 8500 gvw parts and you'll be fine.

Here's picture showing the difference in the spindles. Under 6900 GVW left and over 6900 GVW Right