Cab Mounts with Welded Bolts?

[Orion 762]

I'm trying the 'Replace Cab Mounts" game, but on both of my "forward cab mounts", the long thru-bolts have been welded to the floor (on the inside of the cab). The rear cab-mounts come apart with no problem. (1971 Cheyenne).

I recently bought anew set of mounts/bolt/nuts etc. Do I need to break these welds, OR do I just try to re-use the welded thru-bolts as-is?? It looks like a TIG weld where the original "hex head" of the bolt is melted/welded to the flooring. I guess this was done to keep them from backing off on their own.

Any hints?? If I keep the original welded-in bolts, it looks like I'll have to raise the cab (somehow) more than 4" to get clearance to install the new rubber mounts.

If I need to remove these thru-bolts, what's the best way to "break the old weld" without chewing a hole thru my floor?

Any help will be appreciated.

Orion 762