I'm looking for spec's for a marine application...
Piston to cylinder wall clearences? How do you check them?
This is dependant on the piston you use, for example most mfg will have a chart like this:
http://www.kb-silvolite.com/clearance_pop.phpIt is based on the bore size, usage, and piston silicon content. You check it with a bore gauge kit.
Ring end gaps (file fit rings)? How do you check them?
You check them in the finished bore with a set of feeler gauges.
How do you check for proper pushrod length (aftermarket solid roller retro-fit setup)?
You want about 1-2 threads showing on the adjusters - assuming you have a rocker arm setup that adjusts at the pushrod itself and not at the center. If it is at the center, I don't know.
Lastly, valve to piston clearences, what's a min clearence?
.090 - BTW - Duration has more to do with this clearance number than lift.