Lar45...It will fit with no problems.

The RCBS dies have a small ring right below the groove that the setscrew fits in on old Lyman sizers. This is about .020" high and .125" thick. We've had to turn it off for our nose first sizers but other than that, they're pretty much the same dimensions and interchange.

So are the old Lachmiller dies if you encounter any. I got a batch in a trade last year and they all fit just fine./beagle