mr gasket MLS head gasket for stock block?

I have a couple of questions about The MLS Mr Gasket Head gaskets for Big blocks.
Summit shows a 4.414 mls but says for siamease block.
Then they show a 4.375 for RB.
What is the differance ? Can they be drilled to work?
I am building a 451 with a 400 block tha is .010 over and has some cylinders with large chamfer.
The 1009 felpro looks like it will hang over .
Would like to to put a race gasket on and not have to change the Ra finish on the heads or block.
Any body have experiance with the Mr Gasket MLS?
Thanks .

I've used them when Cometic was making them for MrG, MrG went overseas to have them made since so no input on what thier like now, sorry. All the MLS head gaskets coated with Viton need 50 RA or smoother is what I have seen on the instructions, if not they will leak water out between the block, heads and gaskest Been there, done that Get the surface correct now instead of having to later like I did