Cam grinding

Is it 18 degrees at 1800 rpm? If it is, it likely has a bunch of mechanical in there as well.

You may have a HUGE vacuum leak. Anything that pulls vacuum from the intake, plug it off. Isolate the intake tract. I missed the carb/intake combo, check baseplate and linkage for interference with the intake. Some carbs have a real issue with linkage interference.

That cam is not that big. I've run 284/484 cams, which are big compared to your cam, in a 8:1 340/360 engines and they ran hard. You need to tune the engine up for what it wants, which in your case is a crapload of initial timing, 24* or so.

Don't drive it at all when doing this. Turn it so it has 36 degrees timing at 1800rpm and start turning the idle down. See if you can get control of the idle. Then put a timing light on it and see if any of the 36 degrees dropped out.

I'd mess with the timing before doing a cam swap... it's a BUNCH less expensive!