I was looking to get the TAV's jackshaft plate as well, because the original baja jackshaft is well, kinda messed up. The keyways are all bent and twisted around from the key cleaving off in there once, and I literally put a new key in there and sledehammered it back together. It's holding now, but I highly doubt it would come apart again.
Looking at the parts drawings, it looks that the jackshaft plate was the same for either the 3/4 or 1" kit, so if you've got one you'd like to part with....
Parts seem to still be lying around, so I'll call mfgsupply tomorrow and see if they have the plate-jackshaft parts.