Don't waste your time bolting them in. Buy some 3 X 1.5 tubing and flat plate and no floor mods will be necessary. There are many threads on this if you use the search function.
I see and saw all those threads after I bought the US Car tool ones. I just can't return what I already have because they have been trimmed to fit my floor. I think I am just going to remove the deadening in that area.