Is there a standard deck height on a stock 454?? When I go to use the calculator for compression ratio, Im guessing at the deck height...and I know that makes a big difference because of the area involved. The engine Im getting is stock, never decked...should I figure .020, .030 or more??

Should be .025". However, it can, and likely does, vary from that.

Yup, varies alot.

Factory is usually in the .025" - .030" range. Then depending on what pistons you use, it could add another .010" - .015" on top of that.

Always check it, if you are doing anything where it really matters. Generalizations aren't good enough. Period.

If everything is "to spec" it should be .025". Add up 1/2 the stroke, the rod lenght, and the factory speced pin height then subtract this from the nominal deck to crank centerline dimension and the difference is .025". However, tolerance stacking can cause the actual deck clearence to be different. Very few factory blocks have perfectly square decks at the speced height, there is variation. Rods vary and the stroke varies, all within factory tolerances. Blue printing an engine means correcting these (and many other) deviations from spec.

Anyway, using .025" is as good a value to use as any other. You'll be as close as the factory gets. Rebuilder cast pistons are .020" short on pin height. This will add another .020" to the deck clearence. Many high end 350 pistons are .010" short (for use with a 3.500" crank) adding .010" to the deck. I don't know if this is done with BB pistons.