Those are some great links to canister "rebuilds". One thing that isn't mentioned is the purge valve -- the guy on the Jeep site went looking for a faulty vacuum diaphragm and didn't find it, but there is such a diapragm in the purge valve. If the purge valve is faulty (torn or hardened or holed diaphragm, for example) and doesn't work, there'll be problems. Easy enough to fix on a canister without a built-in purge valve (just replace the valve) but harder on a can with an integral valve.

My van is a ’77 w/ a stock setup.
The can is the same as the one pictured on the jeep site (3 ports, no built-in purge valve, and the "car bowl" port is capped).
Carburetor is a NOS Holley 1945 Economaster and the correct year replacement for my application.
I don’t have nor need to add a purge valve, it’s "built-in" the carburetor, right?