Thanks all, great information. The prices for a lens from that era appear to be high indeed. So perhaps a newer lens is what I'll do. Nathan I do have the bayonet, just not the lens, so apart from the issue of actually mounting the bayonet to a newer lens, and the issue of perhaps not being able to close up the camera as Karl noted above, would a newer 180mm or 150mm give the same results as a period lens? Thanks again everyone.
P.S. Karl, I grew up in SLO too, 1970s, Quintana elementary. Golden age.