Remeber the 7M-G(T)E has head gasket issues
Plus you can make more power from the 5M-GE and if you find 85-86 there is a small difference in power over the 7M-GE but in a lighter Car. I personal like the 5/6M-GE over the 7M-G(T)E engine so thats why I say sit with the factory engine.
But I have heard that there is special type of head for the 7M-G(T)E that will cure the problem, I streed heard.
Good luck in finding that twin turbo kit it sound sweet.
I want a turbo. :D