Tires and Rims Dimensions Help!!

I havea 1965 stock mustang. i had manual drum brakes, and recently had front disc brakes installed.

I had 14" stock rims on it, but my mechanic said those rims will no longer fit, and that i need bigger rims.

My question, what are the max dimensions so i can put the biggest rims on it?

what about these?

http://cgi.ebay.com/ebaymotors/18-P...emQQcategoryZ66484QQitemZ8019246243QQtcZphoto

Any help is appreciated.

Thanks!