How far can you safely mill 440 block deck surfaces? By safely I mean retaining strength et all. And should you then mill the manifold for alignment as you would when milling heads? For example; is it okay to mill the deck surfaces .030"?

I don't think it'll be a strength issue, but I'd mill it square and to spec and not any further.

Manifold side mill = 1.233 x block deck mill.

So if you mill 0.010" of the head you have to mill 0.01233" of the intake side.

http://victorylibrary.com/mopar/intake-mill-c.htm

Yes you can take that much off without issues but you have to make up for it somewhere , either heads or the intake so you just turned a part into something that is only going to fit that head/block combo.

30 taken off would no way be close to making the decks too thin & unless your going w the same head gaskets AND your head/intake port alignment was real good (or close) rather than the compensating figure from the MP bible, I'd set the heads on their gaskets (they only compress a couple of thou when torqued) & then place the intake on & check the port alignment (dykem or magic marker) & scribe some lines & mill either the heads' intake face or the intake & yes alot of intake milling makes that piece to a certain extent pretty much good for that eng only but unless you are changing intakes alot I wouldn't sweat it cause if your heads are assembled/ready you may not want to dissassemble them again to have the intake face milled. The hard part is you are working w the V of these (heads/intake) angles & need to figure the spec to mill the flat surface to make the 2 pieces (intake/head) in a V shape to align but your machine shop should be able to take are of that math for you. If your milling you might as well get the port alignment dead on which'll make your bolt hole alignment perfect.

I hope I didn't miss read something but I do it this way.
I don't do the correction by cutting the intake manifold, I cut the intake side of the cylinder head to correct intake manifold fit. By doing that you can change to different intakes and the manifold won't be engine specific. If you deck your block and heads keep track of what is removed then correct that by cutting the intake surface of the head. Their is a certian amount that needs to be removed on the extreme lower edge of the intake flange that I take off by using a platen surfacer so the intake will set down properly when cut.

logan426