Milling the Heads How much?

here is a few options.
For every .006 you remove 1 cc of chamber volume
Use a steel shim head gasket,normal gaskets can be .045-.060 thick,the steel ones are .025
Replace the valves with thick margin valves to reduce the chamber volume
If the motor is stock,and has never be apart,you could remove the crank and have it offset grinded on the rod journals .030,depending on the amount of deck height you have.This is the distance from the piston at TDC to the deck surface which needs to be checked with a micrometer,and check all of them.
A set of bearing is cheap,100-150$ for good ones,steel gaskets are 30-40$,the crank grinding is about 150$,which will get you the most bang for the buck,as you will gain a .060 stroke advantage,mrmopartech