I've got a race coming up in a few days and have got a 12-3SCT in box ready to be broken in. I forgot to order some Novarossi plugs but have some O'Donnel's 99T plugs. Has anyone used these with this engine, will they work?

I can order in some Novarossi plugs but they won't come in time. There may be some OS plugs available locally but that may be about it...

Also, I read this thread awhile back and recall that the engine is shimmed for 16%. Anyone know how much additional shimming I'd need for 30% at high altitude (about 5000 feet)?

Thx!