Rebuild 904 or swap for 727?

Bob Wilkie said
If I rebuild the 904, what would you recommend I tell the shop who rebuilds it to use or do?

Pretty much a guarantee that they will tell you what they will use. You start telling them you want this or that they’re likely to recommend you do it yourself or you better be prepared to explain to them why you think you need x, y and/or z when they may say you don’t, that they do things their way. Just a touch of reality here, I’d theorize most shops are going to use what they like to use.

Bob Wilkie said
Should I replace the smaller 7260 u-joints and re-use the driveshaft or replace it with a larger one and 7290 u-joints?
If replace, what do you recommend?

Have you looked at what it would cost to change the slip yoke, differential yoke, have a new driveshaft fabricated with new yokes etc?? Just wondering: why are you thinking that you might need to swap out the 7260 yokes/u-joints?
Its your money, but the 7260 setup will be all you will ever need. I’d spend that cash on the converter.