Are there major differences. My 94 Celica GT needs a new engine and I was wondering if the one from a Camry puts out similar performance...

https://en.wikipedia.org/wiki/Toyota_S_engine#5S Wikipedia to the rescue. Some of the power differences lie in the ECM mapping, so if you want the higher output last gen engine you need to grab the wire harness and ECM with it and do a WHOLE swap, not sure how feasible that is. You may find someone here knows about what parts mix n match for the best performance though, like this years cams with that years head etc.

If it's an S series block it'll work.
I put a 94 5sfe engine in a 97 rav 4 that had a 3sfe engine. i'm actually running the 5s on the 3s ecu and wiring harness with 94 5s injectyors!. All on factory.

going from obd1 to obd2, you'll need the wiring harness off the newer motor, you'll need the newer motor oil pump, and newer motor exhaust manifold. Might have to leave the injectors alone, the plug should be the same, but how they machined the heads for the new injectors changed the pocket. should be close enough that the O2 sensors will trim the fuel to work.

Good luck

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to make it easier, stick to same OBD, and get the same 5s for example 92-95 5sfe same any car as long as square spark tubes. If you start going later, its OBDII i believe with COP and you have to plan more.