Not legal advice:
Information included at this site has been derived directly from the Pennsylvania Code, the Commonwealth's official publication of rules and regulations and from the Pennsylvania Bulletin, the Commonwealth's official gazette for information and rulemaking
pacodeandbulletin.gov
§ 67.6. Use of antique and classic registration plates.
No person may operate a vehicle with antique or classic registration plates for commercial purposes or for general daily transportation. Permitted use is limited to participation in club activities, exhibits, tours, parades and similar uses, and for occasional transportation. Occasional transportation means no more than 1 day a week.
And as far as UK MOT or state inspection, PA is in line with UK MOT or even German TUV in principle if you look at the regs, it’s just the inspectors are not as strict so it seems. Delaware is lights, tires, brakes, and emissions. You drive through, they check your lights and tires, you stop on a pad which checks the brakes, and they either scan or run a sniffer if you are older than 96 and check the gas cap (my 993 gas cap failed because it’s sealing ring was perished but really the guy doing it did not have the right adaptor — whatever).
Notably in PA the emissions test for pre-96 is now visual only (and the gas cap I think — mine are always exempt because they go less than 5000 miles a year).