quick tcase question.

I've got an 86 complete with a 2.8 rodknocker,auto and 207 tcase. I'm swapping in a 3.4 as soon as I can clear some space in the shop but I was wondering about the tcase. I've heard the 207 isn't that strong so I've thought about swapping it out as well. I've got a 231 from a 88 blazer sitting in the building and was wondering if it could be used in place of the 207? Or is it even nessesary? I'm going with a 4.5 lift if that makes a difference.