For stiff, you might possibly consider Poly-urethane or Delrin for your bushing material. Complete kits consisting of the entire set of biscuits and sleeves and bolts, etc are available from Energy Suspension, among others.
If you are planning to blow the whole car apart and are not planning on keeping the old body mounts then a battery driven sawzall could be your friend.
Before electing that option I would strongly suggest saturating all the mounting bolts with Deep Creep or PB Blaster or any highly recommended penetrating solution. Don't hit them once, like make it a daily ritual for multiple weeks to soak those bolts. Then use a 6 pt impact socket and the longest power/Johnson bar in 1/2 drive that you have and gently lean on the bolts to see if you have any movement. The bolts themselves are likely to be metric, think 15 mm head and the equiv of about a Gr 5, but they will have suffered a lot of damage or decay and the shank diameter, when you extract one, will likely be a lot thinner than what a new one would be. if you get one to move, however minimal, STOP. Add another spritz of the penetrating oil and move on to the next. No movement, keep dousing them.
A STRONG WARNING AT THIS POINT!!!. Do not mix penetrating fluids and any kind of heat!! Even something as cold as Mapp Gas can cause certain penetrating solutions to "crack" or decompose and some of the chemicals used in them are toxic at the least and potentially lethal in certain instances.
As an example, although not specifically a penetrating solution as such, CRC makes two versions of its brake cleaner, one Red Label and the other Green Label. The principal difference is that the Red version contains CHLORO-FLUORO-CARBONS aka CFC's. In the presence of high heat temperatures, such as what an Oxy/Acetyl Big Red wrench can generate, the CFC will crack and create Chlorine Gas. Totally toxic and highly debilitating.
Knew a bike wrench named Brewdude, Steve Garn, years ago, who had that happen to him while working on a project. He thought he had managed to escape most of the fumes and exposure but it turned out that the real damage hadn't happened immediately! He went to bed and woke up, ( minor miracle in itself), the next day to discover that he was so sick that he ended up in the hospital in intensive care.
The level of exposure, however slight he thought it to be at the time, was sufficient enough that it permanently damaged his lungs and a few other organs into the bargain. He actually wrote a special column for a now defunct magazine that outlined what had happened to him as a warning and benediction to others about the level of hazard and injury that existed. The can labels do carry warnings but the writing is so small most users ignore it. You can go on line and download the Material Safety Data Sheets (MSDS) for the products, penetrating fluids and oils and chemicals; the mfgrs are required to offer a library of them for consumers.
So I guess that the take away here is to either not mix the methods you plan to use to encourage those body bolts to break loose and come out or, if you do, be sure ahead of time that the combination of methods that you go with is benign to your health.
Nick
