Thanks guys, I really appreciate the advice..
As these are going into a boat engine, I suppose I should ask if they would be up to higher than average engine speeds, not so much higher top end, but longer operation at higher revs. The design of boat will mean the engine pulls to 4800rpm but will be used constantly between 4000 and 4800rpm.
With this in mind, what rings would you recommend?
And finally, as the only source for these I can find is in the US, I have two questions...
1) Is there a supplier for these in Europe/UK?
2) If not, is there anywhere in the US that would sell to me at a decent price?
(I'm in Northern Ireland)