As some of you may know I jumped on the back of a group buy organised on the Turbo Minis forum for Protech units. The dimensions I specified came from some kind soul on here measuring a set of AVO or SPAX units for me.
What I ended up with was the following;
400 series.
14.5" open length, 2 1/4" spring seats, M27 upper mount, Bottom mount is 32mm bonded bush with 12mm hole diameter.
The lower mount has a larger than standard hole diameter, you can spec whatever size you want. I'm running 100lb springs which I find plenty firm enough without bouncing off the bump stops.
The fronts are obviously easier to get off the shelf and measured up as;
13" open length, M27 upper mount and bottom mount is 3/8th hole diameter.
Hope that's of some use to somebody.