I used the front bumper mounting locations for my stands. 1/4" plate bolted to the frame with square tubing welded to the plate. THen another 1/4" plate welded to the bottom to mount the casters. My Challenger was hauled from Iowa to Ohio on these with no issues. My Dart was hauled to and from the body shop(1 1/2 hours each way) with them too.

Once my Challenger was painted, I partially assembled the car with them installed. I added larger wheels and some cross braces for my piece of mind. I used a 2x4 to tie the front stands together. It worked fine.