DIYAutoTune has just released a kit with the 56-pin GM connector, enabling you to build a plug-and-play Megasquirt that can be installed in a Turbo Regal without cutting the factory wiring harness:
DIYPNP Delphi 56pin Unassembled Kit DIYAutoTune.com
They are looking for somebody with a mostly stock Regal they can borrow to build and tune a base map, if anybody in the Atlanta area can get with them.
As a disclaimer, I am not associated with DIYAutoTune in any way, other than being a customer (I ran a Megasquirt on a TPI Chevy 350 for a couple of years and bought all my stuff from them) and had been nagging them to offer the 56-pin connector and a case to fit it for awhile.