Is it the rings are worn or dry, or is it possibly the valves stuck open? Remove the spark plugs and put 3 or 4 squirts of oil in each cylinder. Try your compression test again. If compression goes up, then it may be that the cylinders are worn, or it could just have been that they were so dried out they weren't sealing.
If compression is at pretty much zero, even with the oil, then you may have stuck valves. Remove the valve cover, and you can pull any that are obviously down, back up with a small slide hammer. Turn the engine over and repeat the process until they all freely goe down and up. Worst case you have to pull the head and get a valve job, or at least a cleanup.
Chev transmissions are not particularly rare. There is some variation to them with regard to sunchros. All will work.
You can also keep an eye on kijiji or even place an ad looking for a 216 with transmission, or even make the jump to a 235 or a 261.
https://www.kijiji.ca/v-engines-and-...ads/1082366768
The 235 is a fairly direct changeover, the 261 can be a little more complicated unless you are converting the truck to 12V. The ring gears are different between the 6v and the 12 volt vehicles. I have turned the flywheels on the 12 volt to accept the 6 volt ring gear.