I think that in some, if not all years, in which 235/261 engines had front side mounts there were no holes drilled in the lip of the plate under the harmonic balancer which could have been used for the earlier front motor mounts.
I think I recall Pre '68 Dave recently posting a comment that on later 235/261 engines the plate under the harmonic balancer did not even have a lip where front mount holes could be drilled (an older plate had to be used as a replacement for the newer plate?).
