So I have been building an f100 (74') and got some axles dana60/14bolt. I need a motor, its got a gt390 in it but it smokes bad. I figured id go to a diesel but I just installed my 5.13 gears in it!! I kinda wanted to stay with a bulletproof 4 speed behind the truck but with my calculations at 2000 rpm I will only have about 45 mph! My question is how strong are the dodge nv4500 trannies? I dont want to worry about the trans and I can deal with about 55 mph because the most I will do is tow with it if I am not wheeling it.