I was a Ford partsman and HAD a 351C in a 68 Torino which used the early "sandwich" style mount, and pulled many of the FORD ones (presumably built in NA) apart, which always resulted in the fan blade cutting through the upper rad hose.
I drilled and bolted them also ... and never noticed any vibration issues.
Since working for NAPA, I began to notice pictures of motor mounts and similarities in design..
NAPA BKP 602-1151
fit most of the older model Ford 90° and 335 series "small block" engines from about 1966 to 71 in the "B" & "F" bodies (eg. Fairlaine, Torino, Mustang, Comet, Montego, Cougar)
NAPA BKP 602-1253
I'd have a look at these ones which seem to fit the "bigger" B & F series from 72 to 76. (Also 77 - 79 LTD II / Ranchero.)
Here's another possibility:
NAPA BKP 602-1152
1968 - 74 Custom 500