Another Driveshaft question.

So i am getting my 904/7.25 driveshaft cut and having a new one made for my 727/8.25 duster. i know i saw the answer on here before but i cant seem to find it again :( the shop is going to cut off the yoke and ujoint and weld a new tube on. can anyone give me a measurement? also, i would imagine the old driveshaft had a small ujoint. (right?) how hard is it to upgrade to larger ujoint and where would i find the part numbers for that? anything else i might run into? thanks guys, i'll be sure to reward you with some burnout videos when it gets rolling again.