Best spark plugs.

Hi everyone, sorry if this question has been covered (I did do a pretty thorough search). What would be the best spark plugs for our '82 Ski Tique PCM351W. Engine is newly rebuilt (about 12 hours on it) and is all standard (according to our receipts the donk was replaced new in '92 from PCM). It has a Holley 600 Vac Sec and the Prestolite with the breakerless module, Crane coil and no ballast. When I brought the plugs on a quick trip to OZ prior to firing it up they had no plugs specifically for the old Windsor so he gave me a set for a 5.0 EFI (NGK). He said if it starts to miss at high RPM just close the gap up a bit, which it is doing but I haven't taken the plugs out yet. You have to run nearly flat out for half a minute before it misses, and you only have to ease up a bit to stop it. Apart from the missing the engine is a delight. I've got another quick trip to Australia Wednesday so thought I'd ask you guys prior to going. What do you think?

Whats a donk? and no Mik Dundee jokes either.

Be careful with that missing at top end, you could be running lean and burn a piston. My set up is basically the same as yours and I run Autolite 24, after 50 hours this summer they look like new and it never misses a beat at 4800 WOT.

There were a few threads recently about running too hot a plug and lean conditions that ended up in holes in pistons so I would check that out asap. Good luck mate.