here, i used 1010tires.com to come up with these options. obviously the 225/50-15 is going to be the wider of the two. that is the widest tire that you will fit on a stock 15X6.5 wheel, you can fit wider tires on your celica, for example a 235/40-17 (a few celicas on this site have this site without apparent trouble) but this, of course, will require a 17x8 wheel. i know from experience that a 225/50 will cause no rubbing problems whatsoever. my brother has this size on his 90 celi gts.

if you are looking to buy tires, toyo proxes 4's perform and look nice (my bro) as well al falken ziex ze512's which i have, both are all-season tires which i recommend for you since you live in canada
proxes 4

ziex ze512, these are decently priced and were rated #1 by consumers digest a while back i believe