A lot of A bodies from 63 -65 in the US came with the 6 cylinder 4 speed option. It is a good choice for what you want to do because it's what the factory actually offered and these transmissions even though they are just as strong are largely unwanted because of the flange for the ball and trunion drive shaft. this makes them hundreds of dollars cheaper .you're not building a 500 hp thing it's a slant and this A833 will do the job just fine.I've been driving with this set up since the late 70's in 4 different A bodies and never had any issues .It would be worth your while to get a hold of BarracudaJohn