There is a company called Belzona and they make some serious composite materials, adhesives and sealants.... remaining and the dampener was just barely on the end of the crank nub and bolt. I got a new dampener and it slides freely all the way up to the shoulder on the nub. So basically I either need to replace the crank or the engine, unless there's some other way I could manage to get a tight enough fit that it wouldn't spin on the shaft. Any ideas?
I would replace the seal and then get some sort of super Belzona 'glue' and glue that sucker on there and then install a new bolt with Loctite red permanent thread locker.
You said it was running good up to that point, so do a 'permanent pulley installation and drive it till it either gets, God forbid, creamed in an accident, rusts away beyond repair, or has a catastrophic engine failure . THEN, at that point, I'd consider looking at replacing the engine.
It sounds like you take care of your vehicle and are proud of being the original owner. This is not going to make your van a hunk o junk, it is just 'special' now. It'll live on a good useful life with a slight handicap /\...
Alternatively, perhaps you could strike a few dimples into both the shaft surface and the pulley bore with a cold punch. That may give you the slight interference fit you are looking for. [if I could get that to work, I'd locktite the bolt in with the new orange loctite that is 3x stronger than medium but still able to be removed with handtools without heating]