If you intend to keep the car, find a #17 (or later) casting and put the money into that. I would not spend any $$ on a #14 unless you intend to sell the car. The sixth revision of the 603 head is a #22 casting, btw.
Remember that the casting number (stamped into the side of the head, 603-016-22-01) is not the same as the part number you would order from the dealership (603-010-96-20, current wholesale approx $1700, current MBNA list $2140).
If you are short on $$ and your current head is flat, straight, crack-free, and otherwise seems ok... replace the valve stem seals with new OE, re-assemble it, and forget about it. The #14 could last a long time. The valves, guides, and seats rarely need replacement unless something is damaged. These aren't flimsy M103 (300E) heads, lol...
