Our rpmspeed 6.0 gaskets will work great there and are .045 thick which will help with compression ratio also!! no need to spend 100+ on them when these will work great for you

Gasket link

 

What are the specs on the gaskets, are they correct for an over bore 4.030?
Also, who manufactures these gaskets?

 

They are manufactured for us by Victor Reinz.
They will work on a 6.0 or 6.2l with no issue.
They are 4.100 x .045

 

I'd really like to stay with the GM MLS gaskets, so is the LS9 gaskets the way to go?

 

Ls3 head gaskets
In tests the gm are no better than ours and our gaskets are much less expensive.
I use them on all of our builds plus my own personal engines.
They were pushed very hard by a customer in canada. 7800rpm with a 250-300 shot on a 370 in an s10 on some heads up racing for an entire season. Held up and won him his first trophy.

I know some people are GM everything, but gm doesnt make the gaskets. For those head gaskets Victor Reinz makes quite a few of them. A german company makes some also. Keep that in mind. 2018 GM is nothing like 1970 GM.