I assume you have & are keeping the 8 3/4" diff as changing the diff will change the length
the shaft from the 904 will work , it will be approx 4" too long but can be cut down , you will need the larger slip yolk for the 727 though . They used 2 different U joints , the smaller 7260 & the larger 7290 joint , the 7290 would be beter for the 44o but the smaller joint will live as well assuming you are not running high stall converter & slicks