Our '83 E350 chassis didn't have one either but it had an aftermarket kit added by a previous owner.
I imagine the kits aren't as readily available as they were years ago. I'm trying to remember, but my recall is that adding a tank also involved changing to a "recovery" radiator cap. But then again, with so many vehicles having a tank now, most caps are probably OK. Just get the pressure, which I think was the 16-PSI.
Some of the newer Fords have that tank with a pressure cap on it, none on the radiator itself. I recently learned the tank is for "de-gassing" which is intended to separate anything out of the coolant that would form bubbles in the radiator. Sounds like a good idea, but remember the tank is under pressure like a radiator would be. And the tank can crack. I replaced one on a Taurus for a friend at work.
If God's Your Co-Pilot Move Over, jd
2003 Jayco Escapade 31A on 2002 Ford E450 V10 4R100 218" WB