Applied generous amount of Eastwood interior panel rust preventive in the doors and front of quarters (below quarter window). Will do the rear part of the quarter panels (through trunk) and bottom of the panel behind the rear window, pinch weld area inside the roof next.

FWIW, replacement of the four subframe body mounts was relatively easy. Bolts came out with a breaker bar and 1" socket and new rubbers, washers went in place of the old, rotted pieces. If you do this, be sure and note the order of assembly of the rubber, washers, sleeve, and bolt. The front mount rubber is thicker than the rear.

Installed the "mystery trim clips" on both inner door panels, thanks to jamesM. Harold, now we both know where they go.