Great news Leon. I used Race-Mart SFI bellhousing and 130 teeth ring gear to use 904 behind my R5 engine. It worked fine.
Actually I was totally surprised as this 904 hold up so well. I used OEM drums inside, only had manual valvebody with trans brake and TCI racing overhaul kit inside.
Our car was N/A and went all day long very low 9 second passes with bad grip because of slippery race track. It also cost us the car in finals where I totally lost control of a car just after half a track ( terrible tire shake and sliding ) and I made very bad crash...I was lucky to be Ok but the car is wrecked. Engine, tranny and rear end seems to be fine but we need to build new car. Here is a clip of that crash:
https://www.youtube.com/watch?v=WIcvbSy_5kgAnd one video few passes before this crash:
https://www.youtube.com/watch?v=3vf3VpwBxPI
