Hey, what year camrys came with that trans? I wanna rip one out of the junkyard but I need to know what to look for. I assume around the same vintage as 6th gen celica?^^ Untrue. The S54 manual tranny will hold 300 whp all day long. I've seen one holding 433 whp, but you can imagine that the short gearing wasn't suited to match the power too well. You'll need a hybrid clutch for the swap with a 3S pressure plate and a 3S disc with 5S spline, and a stock throw out bearing will work. Southbend Clutch keeps these clutches in stock.
So you CAN just get the engine/harness/ECU, but the 2nd and 3rd gen ECU's have a lot of extra parts. You'll spend a lot of time and extra money trying to track down the extra parts as opposed to just buying a clip. Plus with a clip, you can get the GT4 front end which you can sell to recoup some cash, or you can use it yourself. You can get ST205 brakes, Superstrut suspension, a RHD conversion, and almost everything you need for an AWD conversion that can be sold to get your money back. A clip pays for itself, if you choose to go that route. But it's possible to get the engine/harness/ECU and try to find the rest of the parts from someone else parting out a clip/eBay/etc.
Or, my personal favorite route, and the route I'm taking within the next two months. Get a 4th gen 3S-GTE from an ST215 Caldina. Wiring is difficult so best left to a professional (WireGap does it for $450) but it's the newest revision of the 3S with the strongest block, a newer, faster-spooling turbo, coil-on-plug, and all you need is the engine/harness/ECU and a front mount intercooler. And to top it all off, it's often much cheaper than the other 3S's. You still need a hybrid clutch but the GT's S54 transmission bolts right up.
Anything over 300 whp and you'll want to start looking into an E153 transmission from a Camry or Solara. It's stronger than an S54 and geared longer, which suits the higher power better. At that point you'd need a complete 3S clutch setup with hybrid axles, which aren't as scary as they sound.