[ZacharyDouglas1992]

yeah I figured you did, as your reply was very insightful, I just thought I should clear up a few things for future posts.
Thank you for the links, I will look deeper into them. I also know for a lot of the aftermarket adapters, they are made for the 2wd tailshaft, and the round pattern 205. I will have a 4wd 4L80E, (although I plan to rebuild it so changing the tailshaft isnt a dealbreaker). I do believe, however, that I have the figure 8 style 205. The few sources I have been able to find online say in this instance, my TH400 adapter can be made to work with a little machining, but I am looking for the specifics on that and/or someone who has done this before to possible have me send mine to them.

I will be picking up the new drivetrain this weekend and that will help greatly, as I will have a chance to test fit things and take necessary measurements. Also, whatever I end up doing, I will be sure to keep detailed notes and take pictures of the process, so that at least there will be a source for how to complete one of these many ways to do this swap.