My buddy is thinking about getting an 85 crx 1500 that has a bad head. How hard is it to put a newer 16 valve head on the older 12 valve motor. From what i can see with the head off the pistons are dished to accept the 3 valves per cylinder. The piston to valve clearance is the only real thing that I am worried about. As far as the exhaust manifold goes he has another one he can use.

Are there any other issues that i am overlooking?

Thanks in advance.