Thinned Solid Alum Body Mounts?

[BANKO]

I'm planning on converting my 1965 Chevelle to solid Alum body mounts. Has anyone had their mounts machined to a thinner height to get the body closer to the frame?

I'm planning on going with these parts from ABC Performance:

http://abcperformance.net/body%20mounts.html

What would be the disadvantage of eliminating the body mounts? I plan on converting to rack and pinion along with routing the fuel and brake lines through bulkheads instead of on top of the frame.