Cam for a 318

Pistons are advertised at being 0.012 below the surface, so wouldn't a 0.012" cut do it? I'm buying the heads bare, wouldn't the value seats be uncut for a valve size?

That depends, deck heights can vary from factory and these engines are old and have likeley been opened up and messed with before.
My 318 was a worn 0.040" so I went with +0.060" KB167s, decks were skimmed 0.005" to clean them up and I ended up with the pistons 0.015" ABOVE deck.
Pull the engine down and measure everything before you order your parts for the rebuild.
Sure would suck to assume a std bore and nominal deck height and order +20 KBs to find that it's already +30 and the decks heavily milled wouldn't it? $$$ Down the drain....
You could well find that if it's been opened up and decked before the speed pro hypers at 1.755" compression height might get you close enough for less money - but you won't know until you measure.
The speedmaster bare heads already have seats cut for 2.02/1.6 valves, as I mentioned in your other thread if your chasing port velocity theres no point trying to stuff a smaller valve in with those big runners, Iron 360 heads with 1.88 valve if your set on this (or even reworked 318 heads).
There's many options for cams and you have already had a few good suggestions on this, what heads you run will play a part in selection. Aftermarket alloys flow well at higher lifts so if you go with these look for higher lift cams to get the most out of the heads (higher lift with similar duration to what you would consider with iron heads).
Before I pulled it down I ran a little comp XE250H cam and ported 318 truck heads, headers, 625cfm Carter afb on a weiand action plus manifold and it worked well (not fast but definitely more grunt than a stocker). fell on it's face around 5000rpm but nice up until that point.