What cam to use in a 318

Well, yes to a point. If swapping out the cam it costs no more to order what your engine really needs. The other things I propose as options. If valve to piston clearance is determined to be adequate, higher lift rockers can be installed quickly and easily provided the appropriate valve springs were installed with the cam.
The head upgrades is another minor matter that can be done down the road, possibly as a recondition is required. This narrows the costs difference, which makes the upgrades more affordable. Using readily available Chev valves, springs, retainers and locks also keeps the costs closer.
Just presenting thoughts that someone may find useful.
have you priced machine work lately? and lead times??

i don't know where you are, but in my neck of the woods it's pricey and the lead time is tremendous.

anyway for the type of work you're describing, you'd be in aftermarket head territory-- or darn near.