Nah it's definitely an M6. You can tell by the really angular (80s) cabin architecture.
In terms of the engine, yeah it could be an S38. You guys got that in the States, it was detuned from the Euro-spec M88/3 which had 286 brake. The US catalyst version was actually called the S38B35 which was re-named in the first version of the E34 M5 as the S38B36, making 315BHP.
The catalyst S38B35 in the M6 had 260BHP. I reckon it's a Euro version though...