When you put in a bigger cam you generally need more initial timing to clean up the idle. You did that by switching from ported to manifold vacuum. Adding initial timing also does this but then you may have too much total advance and you may have to recurve the distributor to reduce mechanical advance. If it idles good with manifold advance give it a try. It may work but as you open the throttle manifold vacuum drops and you will loose timing so it may not run well. If you get spark knock then you'll have to get into the distributor at which point you should go back to ported advance and start from there.

Good luck.