Stock crank and rods are specific to the turbo Buick model. In other words if you use normally aspirated rods and a crank they won't last long. The stock turbo Buick crank has rolled edges on each journal to make it stronger.
GN, GNX, Turbo T and T-Types all have the same drive train. However, the GNX has a different center section in the turbo (I think the wheel is ceramic which enables it to spool faster) and a different chip as well as rear supsension and rims.
I've had a turbo Buick for 15 years or so and they are awesome in a straight line but IMO the factory stopping power and handling leave alot to be desired.
I love my LGT. First Suby I ever owned and it's my favorite car...I like it better than any of the GNs I had or my T-Type I have. The LGT stops well and handles (still a ton of room for improvement on the LGT) much better than the Buick.
Frankster is doing a great job. It probably has been covered somewhere in this thread but how heavier is the Buick motor than the Suby motor?