Hmmm. I have a high compression 355 and run the R45S. The R43S was a bit too cold for street driving. The S is an extended tip, the T is a tapered seat . If you have a GM small block, it will not use the tapered seat. You can tell by looking at the spark plug hole base. I would think the tapered seat might let the plug settle deeper but I'm not sure. BTW - I have domed pistons , too, with no clearance problems.
69 RS Conv,355,M20,4.10's and I don't worry about stone chips ( yet ).