Thanks Ron
Speaking with the supplier he's said pretty much what you did.
We've installed a few A500's in A bodys which have the same clearance issues. In those we replace the tunnel sections of the torsion bar x-members with a 1/4" plate shaped to the floor and weld them in.
I can do the same here if a hammer dimple or two won't make the clearance. I don't do rattles or things banging on the floor... weird noises drive me nuts!