I’m doing a head gasket swap on my bored out r53 that’s bored to 77.5 and both the head and block have been machined what head gasket and size should I get?

 

A little more info would be helpful.
- How much was cut from the Head
- How much was cut from the Block

But... In general... If you've taken material from both the Head and the Block, you may want to consider the thicker of your options, if nothing more than to counter balance any increase in compression from the two operations. This will minimise any chance of the ECU not adapting well to any increase in compression, plus possible extra heat created in the combustion chamber from any increase in compression. (Esp since our Head castings are notorious for heat stress cracking)