Frozen Manifold Heat Control Valve

Yup, choose heat-off if it's gotta be one or the other. There's nowhere near as much exhaust restriction in "heat on" as in the V8 valve's "closed" position, so don't worry about it overmuch; the bigger drawback of permanent "heat on" is bitchy carburetion problems—percolation, etc.

Back-and-forth movement is meant to be stopped by clips in the shaft's grooves just outside the manifold, front and back. If grooves are empty, install clips. This in itself can greatly contribute to the valve not sticking!