I guarantee that if it's an MSD pro billet distributor and he used the parts that come with it, it DOES NOT have enough initial timing on it for a 509 camshaft. No way no how at 36 total.
You need one of the bushing I sell to bump initial timing up to the 22-26 range. A stock 340 likes 14-18 initial and you have a BUNCH more cam in the car!
Like you say we need to know the engine specs cam, vacuum, etc.
If we are going to show pictures here is a set of carbs I built for a guy and getting ready to build another set for my friends girls 69 Barracuda.
2 500s and a 350 all pumps and idle circuits.