I have a 91 FC and I was wondering if I can run a 17x9.5 with a 29mm offset 225/50/17in the rear ,and 17x8 with a 31mm offset 225/40/17 in the front... no spacers the car will be lowerd 1 inch. is this a good choice for all around performance?

 

http://fc3spro.com/TECH/MODS/RT/rims.htm

 

225/50/17 is going to be pretty tall/beefy. If your trying to get some nice rubber on there atleast go with a 255/40/17 for the rear.

If you want to compare sizing to whatever you have on now...
willtheyfit.com

 

Your rim sizes seem fine and your front tire sizing also seems ok. But I agree with Mac above, with a 17x9.5 wheel in the rear, 255's would look and perform better as the 225's will probably look slightly stretched and not fill out your wheel wells. I have 225/45/17 on 17x8 +35 front and rear. I like my 45 aspect ratio as it gives the tires a bit more profile than the 40's, but not as obviously tall as the 50's. You'd be running more offset, so the 40's may make more sense for you.