Try and find a core with steel planetries if you can.
Sell your 727 and convertor to pay for the parts of your 904.
Parts I'd buy-
Roller rear support.

re-use your brake or pick up a Griner or similar.

Quality rebuild kit including new bushes and thrusts etc.

If your budget allows an aluminium drum and a hardened Input shaft would be nice.

We usually run a bIgger neck (BW35) as well.
AL.....

Alan Jones