For my 69 Dart, got new mounts and attempted to install with
engine in car. Took both front bottom nuts off (did not loosen trans mount) Could not lift the engine far enough up on the right side for the
lower threaded rod that goes thru the oval frame hole to clear.
Nothing appeared to be hangingup, but could the threaded part itself be
hanging up on the oval hole. Do I need to get a 2 x 4 or
pipe to shift the engine a little?

If I remember correctly, when I did this same swap this same way, I left the mount attached to the K-frame and instead undid the fasteners holding the mount to the engine. Then I carefully lifted up the engine (floor jack with wooden platform, under the oil pan, which was already there supporting the engine while I undid the fasteners) until there was enough clearance for me to wiggle/jiggle the old mount out and the new mount in.

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Too many people who were born on third base actually believe they've hit a triple.

Thanks SlantSix Dan.
I'll give it one more shot and try it this way.
It is the right mount that's giving me the problem,
and it's a tight fit to get those mount to engine bolts off too.