OK then, why is it that I keep asking questions on this forum about my own car yet I get very few replies? dunno...
AWD is possible but you have to fabricate rear suspension crossmember unless you wanna drag over all the gear from a celica and make that fit, or import CAMRY ALLTRAC gear. I guess that the 3s-gte out of a celica should sit on the same mounts as camry but my 3s-fe mounts had to be modified to make my mr2 3s-ge sit properly in the bay. Your camry gearbox should bolt up to the block no worries (my 5 spd did, i guess your auto should) i wouldn't know if the celica GT4 gearbox share the same positioning as camry box mounts in relation to the engine bay. I would happen to agree with wizzfizz on saying leave it fwd. Upgrade to a -ge then boost it later, thats what i'm considering (sc14 from a 1g or a ct28? turbocharger)
Anyhow, I'm one of a few people who have messed around with an sv21, if you want to know of any issues I encountered I'd be more than happy to let you know about this conversion. Just remember though, nothing is ever a simple swap over, you're gunna come across alot of the little unexpected things that'll drive you nuts.