Glad I asked then.
There is a more reasonable method that can be utilized in many cases.
Obviously, the first thing to try is simply removing the bolts almost all the way, then smacking them with a hammer to see if the old mounts just pop out. Some do, most don't...
Check underneath if you have not already for any nuts. No nuts from the factory, but some PO's put them there because they think someone was smoking something and left them off of their particular Bronco.
If you're re-using the hardware (no body lift in other words) then you can use a big punch, or a sacrificial longer bolt threaded most of the way in, then smack away with the hammer. If in doubt in this case, use a bigger hammer!
If any of the four front mounts do not come out the easy way, before you resort to a reciprocating saw, try a drill from straight underneath.
With the bolt completely removed, the only thing holding the lower washer/sleeve/insert/mount thingies in is the mushroomed and rusted interface between the upper and lower sleeves/inserts.
Drilling straight up from underneath with a big enough drill to remove the majority of the material (1/2" bit might be enough, but I think the recommendation is larger, like 9/16" instead) and drill away.
When you drill through to the middle the mount should just fall right out at that point. If not you could punch it out from above.
Takes longer to describe than to do, but drilling has proven to many to be easier to get the business done than a Sawzall trying to cut through the rubber bushings, then the metal sleeves.
Good luck no matter which way you do it. With any luck they'll all just pop right out.
And pigs can fly sometimes too!;D
Paul