904 wont up shift

Sounds like the kickdown linkage isn't adjusted properly or the ratio is way off. It should be all the way back at wide open throttle and maybe just a tad before it. Otherwise things that could cause it would be govenor or valve body valves sticking. If you adjusted the screw on the side of the valve body that hold the throttle pressure valve from coming out then you have effectively raised the pressure, this will delay the upshift no matter what you do to the linkage.

As there are a lot of mismatch parts there and I'm not sure how you put it all together you could also be losing pressure around the reaction shaft seal rings.