yeah i suppose he could just do what you say and remove all the 3rd valves and weld up the port for them.

or he could try and find a used head and put the (correct one) back on the engine to eliminate the headaches in the future just in case someone else works on this engine.

or considering the time and labor costs to do this versus just getting another head

i'd weigh out the differences and see what would be the most efficent route to take. Of course if it were my engine i'd want it right, i'd put it back like factory like it was designed to be in the first place ;o)