Motor swap tips?

[Silverado6.6]

Hey boys, I recently pulled my hurt 400 out and am replacing it w/ a 350 that I'm building...we left the tranny in the truck, and I was just wondering what all tips you all may have for puting the new motor back in and lining it up right so it'll slide right into the tranny, and how hard is it gonna be to get the motor mounts bolted up? This is the first motor swap I've ever done like this and I'm just wanting it to go as smoothly as possible....however, I now know that is IMPOSSIBLE! lol, we originally pulled out my 400 and was gonna drop this 350 back in for a while, and have ended up nearly completely rebuilding it! thanks guys