This is possibly the nerdest thread I've read on this page, and I love every word of it.
I was bored at the shop a few years back, and we started comparing baseplates. I took a sheet of paper and drew long straight line on it. We then placed a given base plate on the paper, so that line ran directly through the center of the two outer most holes. We then traced the base plate on the paper. This gave us a direct visual representation of how/where a give base plates "sits" on your board in relation to other ones. I'll see if I can dig up the tracings. No real surprises, Venture stuck "out" the most, and Thunders the least (stuck out the most on the opposite end).
But back to wheelbase. Not sure what methods people use to measure comparative truck wheelbase, but I basically use the same one as above. It works quite well. Draw a line on sheet of paper. Place truck so that the line goes through inner most holes. Look over truck from above, and mark spot on paper that is directly below center of axle. Measure the distance between that mark, and the hole line, and you've got your comparative numbers (I actually do both sides, and then average).
I noticed that Cast V-5.6s were NOT included in this thread (or I missed it). I have a set. I'll add those numbers later on today.