The early model Sport Pack (SP's) came with 190BHP and ZERO traction control. You have to make up your own traction control sadly,
The only rust the 156 will ever suffer from is along the top edge of the windscreen, this is because the roof was never fully galvanized unlike the rest of the car. Gone are the days mate where you see an Alfa rot away from beneath your feet.
The early models were ALL rated in SP ratings. The SP1 came with black speedo dials, 16" Tele wheels, uprated suspension, and standard cloth seats. The SP2 came with everything the SP1 came with but it had Recaro sports seats which look great. (They are always gray and are identical to the seats found in certain GT's only in fabric instead of leather.) The SP3 came with everything the SP1 came with only it had leather MOMO seats instead.
You can tell a non-SP model a mile off as it won't have the sideskirts, failing that it won't have 16" tele dial wheels it'll only have 15" flat faced pepper pot looking wheels, failing that it WILL have a white speedo backing instead of black. But that's not to knock the non-SP's, ALOT of them came with MOMO leather as it was an option most people took at the dealship. But the non-SP's came with crapper suspension though, but 156 V6's aren't superb handling anyway so if you are keeping one for a long while it's a good investment to improve the suspension anyway.
The Veloce and Lusso models took over from the SP series in about 2000+ I think, Lusso is the sport version and Veloce is the standard version.
But, as long as it has black speedo dials and 16" wheels, you'll have a Sport series 156,
Reliability really isn't that big a deal any more either I'd say, I've had 3 156's and they've all been terrific.