Last night, the fuel tank and lines came out.  The starter button came out, and I disconnected the accelerator pedal. (I'll remove the pedal from the tub *after* the tub is off.)  The only things going through the tub now are the gear shifts.   Looking at those, I either needed to pull the rings holding the boots down (8 screws), or the floor panel (I don't think that exists in an original tub) with around 20 bolts.  Unfortunately, I could only get 7 of the 8 screws out.  So I moved to the panel, and got all but one of the bolts out.  Off to Princess Auto today for some extraction tools.  (I have some--and they did help for some of the bolts, but the remaining one needs something different.)  If extraction doesn't work, I'll just grind the head off.

The more I look at this tub, the more my original idea of getting a whole new replacement tub looks like a good idea.  This thing is rotten almost everywhere!  A new tub is expensive, but it'll take probably hundreds of hours and skills I don't have (yet), not to mention patience I'm not likely to ever have, to do any kind of semi-decent restoration of the tub.  If it was original, I'd probably make the effort to at least try.  But it's not, so I probably won't.