Roy,
50 year old springs and different tire and wheel configurations pretty much makes this very difficult to determine by looking at these old trucks today and measuring them. Additionally rear bumpers were not installed at the factory, they were dealer installed. So bumper type and design will affect the rear bumper to ground dimension.
A while back I was trying to determine the stock factory stance to compare exactly what the drop was on on my 1965 C10 Stepside Shortbed. Here is what I found.
The diagrams below are from GM's archives and they show stock stance for a fleetside and stepside. They don't give the dimensions you're after, but they do give the height of the tail gate in the lowered position which is also the height from the ground to the bed floor. You can use these to compare your current rear stance to stock.
Fleetside Diagram Stepside DiagramNow if you want a semi-accurate front end height dimension you should be measuring the "axle c/l to wheel well opening" which in factory condition is about 18-1/2". I base this on asking fellas with stock trucks for the dimension, which as stated previously, may or may not be accurate.
The reason measuring the height here is important is because rim diameter and tire diameter do not effect this dimension.
Here is a picture of my truck front wheel / fender.... again the 15-1/2" on my truck is going to be 18-1/2" on a "stock truck".
My Truck Lowered 3 inchesHope that helps!
John
