i hav an 03 blazer zr2 that is factory with 10.5in wide bfgoodrich all terrains but i want to fit wider tires..ive seen that people shave down the fender flares in the front but what would i have to do to fit 12in wide tires and would 12inch wide tires fit on the stock rims?

 

You need a 8" wide wheel (or wider) for a 12.50 tire... here is a thread of mine but your fenders will be different with a ZR2.
https://blazerforum.com/forum/paint-body-interior-39/el-cheapo-fender-trimming-job-30332/

 

ive seen people run a 12" wide tire a stock rims, but it is not reccomended also even if you do trim the fender flares and fender with a tire that wide youll still rub the sway bar.