I am seriously looking into upgrading to an overdrive transmission in my '79 Bronco. Usage is mainly street, highway, trail riding, and occasional rock crawling. Locked in the front, LSD in the back, 35" tires, 4.11 gears. Currently running a fuel injected 400 into a rebuilt C6-NP205 combo. The 2 options are pretty clear. Either way it's going to require a custom x-member.

Option 1: 4R70W mated to NP205, adapted to 400's big block bell via Bendtsen's adapter which clocks the entire assembly 12 degrees.
Pros:

• Light rotating mass.
• Can be built up to handle serious power/torque.
• Mates easily to existing NP205 t-case.
• Better fit inside '79 Bronco's trans tunnel.

Cons:

• Bendtsen bellhousing adapter clocks transmission 12 degrees which may cause some interference issues.
• Requires upgrading to EEC-V, CDAN4 strategy, which basically requires building a new engine wiring harness.
• Will require slight upgrading to handle torque level of fuelie 400 (300 hp, 450 ft-lbs).

Option 2: E4OD mated to BW1356.
Pros:

• Direct bolt-on to engine, no bellhousing adapter needed.
• Significantly heavier duty design - could probably run a stock rebuild without any component upgrades.
• Ability to retain 60-pin EEC-IV engine harness since AHACB strategy ECM is still 60-pin EEC-IV.
• Mates with BW1356 with lower crawl ratio than NP205.

Cons:

• May cause interference with trans tunnel in '79 Bronco.
• Will have to give up the venerable gear-driven NP205.

 

The 4R70w also saw lots of use in the early to mid '90s in 5.0 powered trucks so while I don't know an exact catch code I'd be willing to bet there are some MAF PCMs you could use.

That said an E4OD would likely be an easier swap in this case, the tunnel may need some mods but that's low level grunt work compared to rebuilding a trans and fabricating a wiring harness.

 

I dunno, for me building a harness is easy, modifying the tunnel (have no idea what mods are needed) are the tricky part.

I also like the gear driven 205 so that would be my choice.

 

Maybe an AOD? It would keep you from having to deal with electronics.

 

I agree with the AOD suggestion, there's plenty around.