5-speed swap

i have talked with tremec,,,thats is who builds the keisler trany,,,keisler just modifies it to fit any mopar,,tremec told me the small tranny will with hold most any thing,,,i am looking in to the smaller one cause i like the ger ratio better,,,keisler keeps trying to tell me it wont hold up,,,tremec tells me no problem, so dont let them b,s you,,
i currently have a 340 in a 66 barracuda 6;71 blower,33x22 hoosier radials tires street driven car 8 3/4 rear with a 456 gear with a 1965 formulas S barracuda 4 speed tranny has a 3.09 first gear and cruises the interstate at 2800 rpm at 60 mph,,,just under 10 mile per gallon,, bu ide love to try an over drive tranny.....