Agree PB work OK down to 12" or so vacuum. Typically stock is 18+".

The stock cam is probably around 205 degrees @ .050". I would guess you could go up to 220 degrees or so and still have enough vacuum with a stock 440.

Do you know your compression? Too much cam with lower compression can hurt performance so best to stray moderate.

With a bigger cam, re-tuning is needed to get best idle vacuum. Larger cams like more initial ignition advance. 15-20 degrees is common. With the increased initial, you may have to limit mechanical advance (ie weld the slots) to avoid excessive total advance.

Good luck!