The swap mounts should put the engine where it needs to be exactly BUT old cars bend, twist, warp and rot out of position so.... a small amount of “Adjustment” maybe needed. Shim kits normally take care of that.
I like to put studs in the heads. At least the front. But both if possible. There in the way a lot when installing headers but since your going in fresh.... I myself would at least get the header in and then install the front stud.
They also make a gasket change easy IF you need to do one.
