I don’t know PA laws, though I doubt they could be worse than CA. In CA you can swap any NEWER engine out of a vehicle in the same weight-class (i.e. you can’t put a medium-duty commercial class engine in a regular passenger truck, but all ‘cars’ are the same class anyway) into an older chassis IF you put ALL emissions equipment from the car the engine came from into the vehicle receiving the engine. That even includes stuff like the EVAP system back at the fuel tank etc. To become legal the car has to go to a “SMOG REF” who will run over it with a fine-tooth comb, and there are NO smog refs you can buy so you have to get it right. You can fail it and try again though (I don’ t know anybody that passed on the first try). If you pass they put an official BAR sticker on the driver’s door sill that states the vehicle smogs as whatever the engine came from (i.e. my buddy’s '93 FD smogged as a '02 Camaro V8). It’s 100% legal, and from there you are still subject to the regular aftermarket parts rules (i.e. they have to carry CARB EO#s on them). My buddy’s FC that goes 9s has all CARB EO# parts other than the little n20 hit. It actually “only” goes 10.3 or something like that in 100% true legal form.
-TJ