so I caught harbor freight on the way to church and all I found were 600lbs. rated casters
which I do think is beefy enough for an A-body, body shell
On the way out of church, I went to home depot and the heaviest caster they have is only 350 LBS.
so for now I have the 600. lbs. ones
I think the plate steel I have is too thin so I am waiting till tomorrow and see what I find