340 engine/assemble questions

I am almost finished with the assembly of my '70 340 and have 2 questions.

What does the 'R3' mean that is stamped on the front of the block mean?

and

the head gasket (Felpro) has a 2 tabs protruding beyond the head, one in front and one in back, where the intake manifold is supposed to set. What do I do with those? Just trim them off?

Thanks,

Doug