I attempted to use a 1/2inch as that seemed closest but didnt fit exact. I wanted to confirm so I didn't round anything off....Thanks!

 

5/8 I think

 

If 1/2 may be a little large how could 5/8 possibly work?

 

It definitely wont round them!

 

Stock head bolts are 5/8", ARP's 1/2". Use a six point socket.

 

try 12mm if its a little too large

 

Well I used a 1/2 for all mine, does that mean I don't have factory head bolts? 5/8th was too big.

 

I would say yes.

 

This depends on which ARP's were purchased. They also make 12 point, bolts and nuts.

 

damnit, that means someone else has been in here before....The tops of the bolts don't say anything about ARP I have a set of ARP's and they say ARP on the top. these just a have the markings for the bolt grade and some letter.

 

Its like finding our your wife / girlfriend wasnt a virgin

 

It scares me because the car only has 40k and someone must have changed the headgasket once already.

 

If you had no other concerns before this, I would not worry about it.

 

Not surprising, LT1's are famous for having gasket leaks. My 97 had the engine changed at, like, 32,000m. Personally I'm glad someone else had to deal with it.
If you have any contacts or just know a friendly dealer, you can get a print-out of all warranty work that's been done on your car.

 

Maybe that is why your headgasket is bad right now, maybe the previous owner botched the repair. Get it done right and be done with it.