Originally Posted by ELMACHOGERACHO
i know that the 96-97 heads are different from the 98-03 heads
I don't think you have the years right. Somewhere in the 1997 model year the heads had the diameter of the spring seat reduced around the guide (that'* why the LS6 springs don't fit some earlier heads), also the head and valve seats was slightly reconfigured to reduce the likelyhood of cracking the intake and exhaust valves. Doesn't mean to say the later heads don't crack because they certainly do.