When I did my swp, I pulled the trans and transfercase together, since I had done it a few times in the previuos monnths before the swap. Having my truck lifted made it bit of a pian at first but after using the engine hoist to help lower it to the ground through the shifter hole in the floor, it made for cake.
But when I went to instal my 302, I did the engine and trans minus the transfercase, since the transfercase wouldnt fit throught the tunnel.
I do agree, with the core support, it will make for a bit of hell to instal both the engine and trans together. But knowing that I was going to have to cut the core out a bit for the rad, I just decided to cut it out where the rad mounted. It was one of those "Im designing everything as I go" kind of things once I got to the rad.
More pics of mine start on page 66 of my build thread