OK so you have:
56H Pri jets (51H stock)
.038 PVCR ie stock Holley
#59 secondary plate (stock), my calcs say that's a 58H jet but not a lot of difference there
So OVERALL your carb seems a little rich (way rich with those 60H jets in it) but even with the 56H in there, given you have headers, it should not be rich enough to run "badly". Maybe a little slow but should run good.
To tune it much more will take some timing setup, GTECH or dragstrip or other then you can dial the jets in, and eventually the secondary.
Meanwhile I would still try locking the secondary shut just cuz its easy to try, see if that improves it.
And of course, make sure the floats are set right wet.
Is your carb on the car mounted front-to-rear like a v8 or side-to-side (like mine). Not sure it matters but that's 1 more variable.
