Wow! Memories there! Back in the day I had an 85 T that I did a very similar relo on the turbo to. I hacked up a set of KB headers that I got, used an 87 turbo and a turbo bell from Rick Head over at Turbonetics (when he was still there--yeah, that long ago). On the intake I sealed the rear inlet using a large core plug and JB Weld IIRC. I cut the top of the manifold off (where the power 6 emblem is) and welded a "box" on top so that I could use an 86-87 upper plenum and tb. Worked absolutely bitchen and got me into the low 12's. No, I have no pictures (and I still have not figured out why that is). I now have an 85 dirvetrain in a 1980 4 door Cutlass (John Kilgore's car). I have been away for a loooong time but I'm getting back into the turbo Buick game again. I'm going to see what I can work out for a downpipe (without the elbow) first and then go from there.
Just FYI, after the 85 T went down the road I got a Toyota Supra. Started modding those cars heavily and actually still have my brown 89 that has run a best of an 11.78. Made lots of custom and "one off" parts for them. My other red 89 Supra currently has a transplanted 1U (V8 from a Lexus LS400) in it. I picked up a 2004 GTP about 2 years ago that I have modded a pretty good amount and that made me want to get back into the Buick game.
It's good to be "home".
-Dean