I would stick with 55 series to avoid the speedo calibration problems from fitting 60's.
I did post last week asking if it was possible to recalibrate electronically via Testbook/Rovacom but from the lack of responses I guess no one knows.
In terms of tyre pattern and brand, yes Pirelli Scorpion ST's were original fitment, but are getting rarer than hen's teeth. I managed to pick up a couple new old stock on ebay a few months back but haven't seen any since. The STR's that were supposed to be a direct replacement seem to be rubbish on P38's from all the posts around here, so it needs to be something else.... you pays your money and takes your choice but there's plenty of people on here running a wide variety and their opinions worth reading cause the outcomes seem to be quite consistant.