People started cussing the 727 when they tried to put them into the 63 66 abodies. They lost patience. Gotta cut the bellhousing floor bumps and notch the trans rib. And the guys who did manage fitting them in used the big converter and usually didn't hook up their kickdown. Shifted it 'manually'. I built my 904 for my 66 with the TransGo shift kit rv heavy duty, with red eagles and 2.74 first, but it's behind a stock 360 and a 7 1/4 rearend. Plus it was in the car already. My magnum 5.9 will be in front of a 727 and 8.8. Some people have good luck with 904's but unless you're racing, you'll be way ahead in the long run with a 727. 904's were only available behind slant sixes when they first came out; for a reason.