I ordered a new rocker panel for my '70 C10 from LMC and the thickness was close to, if not the same as the original. The fit was almost dead on; required only a small amount of hammer work to form a perfect fit.
Cribb66, I would assume the same to be true for you. Just remember, every truck is a little different so you will have to do some fitting with any replacement panels to get them to line up just right.
This may sound obvious, but never cut anything until you have the new panels in hand and can see exactly where you need to cut for a good fit with the new pieces.
