Exhaust clearance

Bashed my exhaust up into the floor wheeling last weekend.

Bent it back down with a crowbar, but was curious if there's a guideline for how much space you should have between the muffler or cat and the floor

Thanks

I'd like to add a question here, as I recently discovered that both my 87 rigs have barely a 1/4 of clearance from the gas tank to the exhaust pipe and it looks like they came that way OEM :gag:

To answer your question I would think a good 2"s? But that is partly to give the cat converter 1-2"s??? as it is the hottest part under there.