If I switch from a stock yoke to a 1350 yoke will the overall length of the drivshaft need to change? Also, do all aftermarket 1350 yokes have the same fore-aft length?

When I changed from 1310's to 1350's, my new driveshaft was about 1" shorter fwiw.

No, not all aftermarket 1350 GM yokes are the same length. For example, look at a Mark Williams catalog. They have part #39006 and #39038, 1350 series 30 spline GM 12 bolt yokes. One is 3-7/8" long and the other is 2-7/8" long. I believe the standard is the shorter one though.