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I don't think the R/T gaskets would differ from the Mark3 or SCR type.
There was a difference though in the way 450s were made, and this would affect the centre gasket. Early 450 had locating dowels on each side (front & back) of cylinder mouth. Later had the dowels in completely different positions ...

Every single engine I've worked on (about 10) had scoring on the RH end of the crankshaft, where it runs in a bush. Doing nothing about it had no bad consequences. These are very low pressure oil systems, a result of the roller bearing bigend, as distinct from plain bearing.

Well, its styling is dated, but still quite lovely in its way.
Interesting that the 250 version ("Monza") was selling in Sydney Australia for less than the cost of a Honda CB250, when they were both new.
Would you swap for the Honda now?

If you have a widecase engine, that rules out using a frame designed for narrowcase engines (eg, Mach 1).
You could use a Mark 3 frame ("road" type), or an SCR ("trail bike" type).
An R/T frame would also fit.
The road-type frames had a few variations amongst themselves, mainly more gussetting for ...