12" rims will DEFINITELY wear out the front end of your truck! FAST![img]/wwwthreads_images/icons/frown.gif[/img]
The 10" you have are not nearly as bad, but still will also wear it out faster than the stock 6.5" or 7.5" that it came with.
For aftermarket rims 8"s are the best to your front end.
check this out http://www.fly-n-hi.com/gmifs.html