I'm sure there is a way around the build table
Shouldn't be a big problem setting the brackets up with just studding, that is how I di my front brackets - measure 50 times weld once
Anyhow, I've attached my jig dimensions below. The two holes in red are the rear suspension mount positions. The vertical positions are from the build table (i.e. bottom of your chassis rails) so you should be able to work back from there. Hope that is some use
Cheers
Dave