Manual to auto with a 250

[j33p3r]

My 68 GMC has the 250 6 cyl with 4 speed trans. I'd like to swap to a V8 and TH350 which I've found plenty of help with on this site. For now I'm just going to swap the trans. I plan on using a floor shifter and know I'll need the crossmember, aux cooling, etc. My main question is I've read on here that with a V8 swap I should move the motor forward to the holes that already exist. With just the trans swap, should I go ahead and do that now to avoid having to get another new driveshaft later?