I am not sure, but I think that Venture and McGregor are related. I seem to remember those designs merging at some point. McGregor is a presently operating manufacturer.
Many boat parts are not particular to manufacturers and can be be found by searching West, Defender, JSI, etc.
Things like pulpits are simply stock stainless tubing, placed in a bender and bent to fit your boat. For supporting stanchions on the pulpits, there are "t" fittings available to tie into the pulpit and angled stanchion bases to help.
This is one of the fun parts of owning an older boat. You get to meet lots of new people.