I had a TH350 built for my old TJ with a LS 5.3 many years ago. I added a manual valve body with engine braking and it worked well in that aspect. Loved the engine braking on steep hills and drops.
I just thought I'd document my build of a TH350 that's going to be used for wheelin. I'm going to be running a 2003 GM 5.3l V8, TH350 and a 4.3 Atlas in a TJ Wrangler. I have never had good luck with auto trannys from the muscle car days and have been reluctant to wheel anything with an auto...
www.rme4x4.com
I will say, I wish I'd had used a 4l60E for a deeper first gear and the overdrive. Mine wasn't a street rig either, but having OD sure has been nice in my current TJ.
My old TJ felt like it lacked gearing in low range, during certain situations. I had a 4.3 ratio Atlas and when I needed instant wheel speed and RPM, it didn't have it. A higher stall convertor would have helped too. I had a 2000 RPM stall, should have done 2500 RPM IMO.