727 modifications .....

Always seem to have issues with servo pistons, esp. the low-reverse. This happens do to wear over the years and higher than stock line presure. The pistons bind and crack and or tear seals.

There is a lot you can do to a 904 and a 727, depends on budget etc. If the trans is completely apart go with 12 springs in the front drum, a 4.2 intermediate shift lever, a HD 2nd band strut, and a billet low reverse piston kit. And at least a bolt in sprag.

I also like the koleen clutchs and new race plates, and kevlar solid bands, NOT flex bands,

There is a lot more, but this should be more than enough for you, unless you want a 2k+ trans. You can get into drum piston mods, bigger planetaries, front pump mods etc.

Other than than make sure all the seals , bushings, thrust washers, and seal rings are new and tha the clearances are in specs. A sloppy trans will still probably hold toghter for you, but the shifts will be less than perfect,

good luck! 8)