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The 487X heads are better than the 487 heads but aren't really worth pumping a lot of dough into. 76cc chambers and probably 1.94 valves. You will probably have to replace all of the seats along with the guides. I'm sure you will need a set of valves and probably springs (even so if they don't match your cam specs). You'll have to do quite a bit of porting to make them performance worthy heads. If you can't do the work yourself add in the cost of labor and then admire your very expensive low performance heads. So basically get a chain and bolt it to the heads and put them in your boat so you can anchor it down good