DR size, only used at track?

i searched the forums but got inconclusive answers. I just got myexhaust on, bbk lts, O/R x-pipe and dumped 40 flows. now i cant keep traction, I've done enough reading and talking to people and have decided on nitto 555Rs. the questions i have are: will 275s fit my otherwise stock 83 GT without modification? should i get the 275s over the 245s? (I'm definately not done modding yet) and should i get the largest side wall or smallest? The tires will only be on at the track, maybe to and from.
Thanks,
AJ

right now i do have 16 inch rims, but I was only going to use them at the track, and get a set of extra rims anyway. Will the 245s be enough traction for future mods? i've never used DRs before so i really don't know how much more traction they get.
i'll probally try to get around 300 hp within the next year, so more than 300 ft/lbs (i think).