I have a 2004 Pontiac GTO. I have a set of (243) heads off of an 03 Z06.

ARP's bolts list for 98-03 LS engines, where all but 2 bolts are the same length. For 04 and up it lists a different part number and all of the bolts are the same length.

Which ones do I use? Why the difference? Thanks.

 

You have a 04 block, so get the bolts for 04 an up.

 

Not necessarily. Some of the 04 goats had blocks with the short two bolts in them. I've seen each case in 04's. You will prob need to removed either the front or back bolt in the center row of head bolts to see if you need to order the 04 and up or 03 and lower.

 

Are you going to pay for the restocking fee when he has to send them back?

My 04 LS6 used the older style. You must verify the bolt holes before ordering.

 

Sorry, my bad!

You would think there would be some type of identification on the block you could use; without disassembly.

 

To be sure, you'll need to use a dowel rod to "plumb" each of the outer end top row M11 bolt holes and compare it to any of the other M11 bolt holes. Early blocks will be different while later blocks will measure the same. You'd prolly get by OK just pulling a single bolt from two different locations for comparing, then putting a mild retorque on them until your parts get to you. I know the purists will have a hissy-fit about reusing the factory bolts, but I'd do it for this temporary basis without a second thought...

 

Some vendors, Summit Racing for example, will let you return unused parts with no questions, no prior authorization, and no restocking fee. So, if you are willing to handle the return shipping cost and pay (temporarily) for the part you can work around the problem.