As has been mentioned, they're supposed to be done on the rack...... a drive on rack.
You could do it if you had a pit as well. Those are the two ways that for sure will keep you
out of trouble.
I've seen it done on a flat floor with like 6 or 7 of those cement 12x12's under all four tires.
(I'd definitely have jack stands in "catch mode" with this concept though)
We always MIG'd them on Mustangs but on some of the newer cars with HSS floors we TIG'd
subframes. (like on newer Camaros, etc)
ex-Global West GM
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