I did the 3sge swap and I widened the rear track width to accomodate the slightly longer cv shafts. I might have got away with not doing that but it would be very very marginal. They fit straight in the hubs but remember it was the non-turbo shafts the turbo ones may be different (not sure though). Also the all-trac is 4wd and has a different box with the rear driveshaft as already mentioned, they are worth good coin to the street racers that blow them doing drags so you could probably sell it and buy a mr2 box with some money to spare.
You will find if you are not comfortable with wiring that you either have to get comfortable or find someone who will wire it for you at a good price. If it was a MR2 turbo motor you can buy the adapter for the harness but the celica has an intergrated fuse box on it so it is chop and start again on the body loom side. It took me about 20 hours to wire mine using the diagrams. Someone who knows what they are doing will take less but I was a celica loom noob so had to reference every wire.
I have it posted on here, it is not a step by step how to but it has the ghetto shifter and shows the engine in place with a quick video of it running. Mine was a ultra budget build hence why I didn't use a turbo motor it is relivant all the same I know a lot more about wiring than before at least. Remember to put the dipstick in before you drive it as well
MK1.5 build