Originally, from looking at some of the photos of the GM Tri-Y headers, they looked to have short sections before the first merge, and looked to maybe easier to fit, but the lengths Pipe max is giving me are near 20" to the first "y", and at that point, it may be easier to fit a 4-1 configuration?

Anyone have information on what merge angles to use for the 2-1 merges?
Several look like 45-degree? or would a shallower 30-degree be better?