I'm assuming it's probably a small block V-8 in your truck. And I also think they were still using points in 1972. If that's the case first I would check dwell to make sure points are set correctly(a visual inspection of them is not a bad idea either), I think it should be around 30 degrees but I don't have specs handy. When your dwell is set then you need to check your base timing by disconnecting vacuum to distributor and checking timing marks with timing light. I think you should be around 4 or 6 deg. BTDC. If all that's good and it's still pinging you might want to get specs and check what total advance for your application should be. Also get some fresh gas, maybe you got some bad gas(happens). And I'm pretty sure your vacuum hose goes to ported vacuum(like you described), at least it does on all my Fords.
BUILT FORD TOUGH