The castings are the same. The combustion chamber on the 2.02 heads have some machine work done to unshroud the intake valve. It is fairly easy to have the 1.94 heads machined for the 2.02 valves and be correct. A lot of the time the original 2.02 valve heads have had a valve job or more and the seats are deeper in the head so a rebuilt 1.94 is more desireable.
X2 on this idea....I replaced the heads on my Z28 with a good used set of 291's with the 1.94/1.50 valves.....even found the right cast dates. Had the machinist replace the old valves with new 2.02/1.60 valves and had him to unshroud the intakes. Those heads looked like new ones when I got them back.