Thermostat housing on a LD 340 intake

I'm having doubts if there'd be enough clearance to run a 7/16 bolt or stud through the thermostat housing and still have enough room to turn the hex- you're talking a 5/6 (bolt)-11/16 (nut) head size there. You MIGHT be able to use a socket head allen screw there- the heads are slightly smaller.
Rusty's correct- that manifold is worth fixing right. At a bare minimum, Loctite a couple lengths of aluminum threaded rod in there, and drill it out to the correct size. Redneck, but it works.