Long duration cam in /6

I would imagine the stock 340 valve spring would suffice for most all but the most radical cams for your application. You can get a generic brand 340 spring for like 40 bucks.....course that'll be 16 and not 12, but that's ok. As for valve size, there's really only like one popular oversize I think it's like a 1.74 intake valve...i forget the exhaust size. No doubt you could go bigger, but first, I don't think it's necessary and secondly, you'd be lookin at more cost as that first oversize is really popular and inexpensive. As for compression, you just need to decide what you want there. the slant head will take a .100" cut off the deck surface real easy. Some folks go more. some take half off the head and half off the block. The end result is the same. I think going .100 off the head and them thin steel head gaskets like Charlie S has will get you around 9.5:1. that's plenty.