I read on here that Series I TB'* are smaller than Series II'*. What are the interchangability options (if there are any) for the TB'* between I and II? Idealy I wanna move up to a larger TB on my SSEi for some more air flow?

i dont think that the SI and the SII are interchangeable. you could always P&P it

Zero interchangability without a substantial custom adapter plate. The studs are in the wrong locations, and the bore is way off the diameter of the input plenum on the M62. This would require heavy rework on the SC itself, and would also require a very expensive AFC calibrator be installed. Your MAF can't handle that flow. It'* out of range.

Even the simple upgrade to the 94/95 SC from the 92/93 requires an AFC calibrator to make it work.