Tranny Recommendations for 600 HP

I have run a 904 and 372 stroker for almost 7 years on the street. Motor dynoed at 540 and the 904 was built with all the above mentioned parts. This is in a 65 Valiant full interior street car with 4:30 gears and it is the tamest motor I have ever had with a solid roller cam. Reverse manual valve body 27" drag radials and car runs mid elevens through mufflers and on pump gas. Holley 750 with Victor intake and RPM ported heads. The 904 has been bullet proof and also weighs less than a 727. My mother could drive this car if I could teach her how to shift backwards. The 904 has never been opened up since it was built, 3000 stall. I would probably not build a 727 unless it was behind a big block with more torque than 500 and horses above 550 - 600.