256H is a very small cam for a 351C - 206/206 @ .050" , .468/.468 lift - vacuum reading should be higher at 12* static timing.
I see no reason it shouldn't be able to manage up around 18" of vacuum, but that also depends on static timing and how you have the carb tuned. If you have tweaked and tuned it and the BEST it can manage is 14", you definitely have something going on, whether it's worn rings, bad valves seats etc.
As far as the oil loss, it could be pulling it from under the intake. If you have a friend follow you, let off the gas at 30-40mph and downshift to second. If it puffs a bunch of gray smoke out the tailpipes, then you have either an intake leak, or your rings are giving up the ghost.
too many variables to tell if its good or bad
my bone stock 351C 2V with 110K on the clock. my timing at 9 BTDC
vacuum is 20 in park and 17 in drive
when RPM increased the vacuum should go down
my vac gauge is connect to the ported carb port not direct manifold and I have that vacuum tree thingy on the water pump disconnected.
Vacuum gauge should always go on manifold vacuum, ported vacuum is 0 at idle.
that seems way low
should be 6 initial for factory
. my engine likes a little more.
and 38 total
you need to get your dizzy checked out and calibrated,
Agree his total timing is low, but let's focus on the oil consumption/low vacuum issue, as distributor calibration/total timing has nothing to do with idle vacuum readings.