I am too, and I'll run a time ticket on the job so should be able to get pretty close on costs. Looking at online photos side bolt bosses seem to be pretty common and well laid out so the mounts may not even be an issue. The rear plate *may* need to be re-drilled but I sort of doubt it. The damper could be an issue for the hydraulic drive but hopefully they used the same crank. That leaves the compression ratio. Propane can commonly run 11:1 and maybe higher but I think the high compression car engine is about 9:1 but I don't know what they used in their forklift engines. The cams are probably different too. I'd think the forklift engine would emphasize torque but I'm willing to try it.

One other detail, is the jet valve common in car engines for emissions, but I don't think that will hurt anything as long as the rest of the engine is built for it. Might be a problem if swapping heads though.

Jim