Slumlord. So much depends upon condition. IF the thermostat housing gasket surface is not eroded, all of the threads are intact (especially the threads for the thermostat housing), the hold-down ears haven't been welded back on, the bottom of the intake is not cracked where the choke heat tubes go across, and the choke hot air tubes don't need to be replaced, $300 is the price I would expect to see it sold for. The right person may pay more.
Don't forget that they need an appropriate valley pan for the Ford 2x4 intake . . .
B manifolds have been bringing prices over $300 on a regular basis in the bead blasted and repainted condition! WoW!
In following this stuff, it seems that an awful lot of dual quad intakes and set-ups have been surfacing in the last year on eBay. I wonder if the stuff is getting o-l-d and individuals or their relatives are cleaning house.
Hope this helps.
NoShortcuts
a.k.a. Charlie Brown
near Syracuse, New York