How far should the drive shaft go i

[jason6101188]

I got a 50 gmc that i just got done putting a 350 and 700r4 in it. I got the engine crossmeber and mounts and the trans crossmeber in place and the engine is bolted up but the drive shaft is going into the trans about 2 3/4 inches is that good or if it isn't what do i have to do to get it right.