Currently I am runnuing a 8# 8rib setup. I would like to go up to 12-15# but I have been told to switch to a 12rib setup with that much boost. I measured the pulleys and they are just around 1" wide, but my idler pulley is 1.625 wide.
So I was wondering the width on the 12 rib to see if I have to change that too? Also is there alot of modifying the fan ***. to get this to fit? Thanks for any replies in advance.....John

 

Yes you are going to have to mod the drvr side fan to fit the 12 rib. I would recomend getting the 12rin also.

 

The idler definitely needs changed as well....

A 12 rib is approx 1.65" wide.