Grant Erwin wrote:

Well, here's what I *know*. I drilled the bolt pattern to the second
set of dimensions I posted and the plate fit perfectly. I drilled 1/2"
holes. And in my manual (M-105K, the last and most recent Bridgeport
manual) the hole patterns appear different for the J and 2J heads.

There may be different ways of measuring the bolt centers, but as far as
I can tell, the
main head casting is the SAME for both 1J and 2J heads.

Jon