What is the complete casting number under valve cover.
462624 is open chamber 76cc low perf crap cracks bad ports like light weight 882 some have tiny valves too.
Some have 2.02x 160 valves but still crap. no power.
Marine version may or may not have hardened exhaust seat insert.
Check for cracks before investing $$$
If you want power find a better cylinder head.
"624" on underside intake runner is a 305 head much like a 4416 head.
small 58ish cc chamber 1.94x 1.50 valve. needs porting and larger valves for a 350.