What motor to go with?

Can't say to much bad about a 904 if it's done right.

My buddy's Duster had one in it and it took over a year of beating the sh** out of it for the 904 give up. That was a little over stock rebuild. If a guy knows what he is doing, a 904 is a really good transmission. It takes close to 50hp to turn a 727 as to where a 904 only takes about 25. More hp/tq to the wheels FTW!