Sand blasting will warp if the blaster is not skilled. However the thicker gauge metal in the AD makes it less susceptible to warping than later vehicles. I had mine sand blasted by an experienced restoration shop and have had no problems.
The frame can be blasted by any yokel without harm.
If I had it to do over I would have it dipped. That is a more perfect method, more expensive but better results. With the blasting you should remove every part completly to get sand into all crevasses. My frame, when blasted consisted of 3 crossmembers and the rails period.
And tell your dad to do it all because you won't get another chance.MHO
