Oh yes, the “V” of the V8 starts changing.
Think of as if you went way down the V, the interesting
Line get closer together until they meet.
True, depends just how OCD you are and how much time you spend picking fly specs out of your black pepper.
Also on your $$$$$.
Worked on an FE a couple years ago being the valve cover rail is part on the head and part on the intake, there was a mismatch between the two after the block was decked. The intake had to be cut to get rid of the step in the valve cover rail. Most other engines would just be a port mismatch. Without gasket matching intake and head ports there is probably a little mismatch anyway.
Those intakes are an odd mate up, but kind of cool.
Gives a narrow head, so putting on an aluminum intake cuts motor weight.
But a vacuum leak will suck oil 
Yeah, you’ll want to have the intake machined to match the heads/block machining. This is for sealing, and as Larry stated yes, the “v” starts to change because the height to the deck where the heads mount is actually getting shorter. So is the distance across the block as well as the distance from one head to another. This applies to ANY “v” engine regardless of make. You used to be able to tell when someone cheaped out on this at swap meets because they would have their new aluminum intake that didn’t seal for sale with the bolt holes slotted 
.