I don't know all the rules and regulations regarding emissions. I do know that you are not suppose to tamper with them to the tune of some significant fines.
I know a whole lot of people breaking these laws and none that have been caught. Each State that performs inspections do them different. Keep that in mind while reading any posts to your subject.
Usually, you can't go wrong by running a "newer" style engine than the one you have. In your case, chances are a 1988 T.P.I engine with cats would not only run better and faster, but would surely have cleaner emissions than your original motor.
You get into trouble when you go with aftermarket or older engine designes that do not include provisions for an E.G.R. valve, or have so much overlap on the cam that they would never pass an emissions test.
There are plenty of specialty companies that work within the legal guidelines to boost power.
You may not be able to buy a crate motor, but rather speed parts that are certified 50 state legal. Crane makes some great emissions legal cams, there are plenty of emission legal aftermarket heads and intakes. The final part being your intake and carb. You can always juice up the ignition with no damage to the exhaust, and you can install 50 state legal A.I.R. headers with after cat pipes and mufflers. Electric fans, free flow air cleaners, and other small goodies like roller rockers can boost or free up horse power without damaging the emissions.
The thing you would be looking for on a crate motor is the cam profile and if the heads have provisions for the E.G.R. Most crate engines leave you to choose your own intake, carb, ignition, and headers anyway.
Don't know if I helped you or not.
Chris