My 440 build

Don't sweat the chamfer. Some of it will be taken down by boring and decking, but in the grand scheme of things, it might drop your compression a tenth, maaaybe two? Use the affordable and very good fel-pro 8519 head gaskets (4.505 bore size) and no worries. The cam you listed is small for a stroker, especially at that compression ratio. I don't mean small as in 'weak', but small as in 'too much cylinder pressure'. If it's a streeter, why risk it for very little reward? You can make great torque and power without taking it to the edge. Personally...and this is just my opinion, but I'd look for a piston with some dish to it, then you can get away with a milder cam. The best thing at this point is to have a good heart-to-heart with your builder and be honest about your intended usage.
The thing about the later blocks (I'm currently building a '78 block into 505" myself) is the decks usually aren't square (not even close!). Have your machinist "square deck" it to get them the same height front to rear on both sides. It typically costs a little extra but it's well worth it!

(Mine's over on FBBO, good toilet reading if you're gonna be in there awhile:D)
New build. 505"