Anyone know what the thread size is in the block ? I want to get a tap to clean them up when I'm re-building.

I think its either M11 x 1.5 or M11 x 1.75 ??

Anyone know for sure ?

I dont have any original head bolts to cut and use, and getting some here in the UK wont be easy.

 

You have to order the speacial LS-1 specific tap from ARP. The holes are roll threaded, and using a normal tap will cut off the rolls, causing weakend threads. Summit should carry it, but you'll prolly have to call and specify it.

 

I hear you, but that doesnt help.

I would never order anything direct from Summit. They may carry good stocks, but for international orders, they suck.
Extra surcharges, and extortionate shipping costs make them a no go.

 

You can get it direct from ARP for $40-$50 + shipping.