Question: Tire Sizes and that sorta fun stuff

[Reese001]

Hello everyone it’s been a while since I posted but anyways I have a few questions about tire sizes and what not because on my 1974 corvette the tires are slightly too wide and have done damage to the car and I am in the market for new tires. Since I am stripping the car to bare fiberglass with the help of a local shop which is run by some of the best guys you could ever hope to have working on your vette or any-other car for that matter. But anyways back to business.

I am looking at a car set of Crager S/S’s from summit racing the 617834P
http://www.summitracing.com/parts/CRR-617834P/
or
American Racing Torq thrust 2's with the same set up pretty much.
http://www.summitracing.com/parts/ARE-5057861/
whats the diff between the 4.5 inch backspacing on the cragers and the 4 inch backspacing on the Torq's?

Those to be specific anyways I believe I have done all the research I need and would like some opinions on how you all think these rims will work with
245/45/17’s in the front
255/50/17’s in the rear
What’s everyone’s opinion on this setup? Do both tires the same size or will having those sizes in the front and rear work well to avoid further body damage? Anyways thanks for your time and here are a few pictures of my progress with the vette.
http://img714.imageshack.us/img714/2193/img0025.jpg
http://img718.imageshack.us/img718/6370/img0021g.jpg
the rear end is completely down to fibreglass except the rear bumper which is urathane(sp?) so i would say the entire left side and rear deck area are pretty much stripped and ready to go, the hood, t-tops, and rightside have yet to be touched(door forward) anyways I am having a blast doing all this stuff and the owner of the shop is an awesome for teaching me and helping me with this project.
and as a side note I am 90% sure the future color of this vette will be emerald green.
anyways sorry for the block of text and thanks for all your help guys

 

[raybies]

backspacing is the distance from the inside of the bolt flange to the inside of the bead area on the rim or wheel.
In your case the difference between the 2 wheels is a half an inch.
as far as tire comparisons here is a link that gives you conversions and exact specifications for almost any tire, and lets you compare the diameters and so forth, it will even tell you how far off your speedo will be with the various tire sizes.
Tire Size Calculator - tire & wheel plus sizing