I have got a 1968 440 engine that was put together by a machine shop 15 years ago. So I took it down to check everything and found the Deck surfacing machine Job was messed up. So I took it to my local shop to get cleaned up. They took .020 off to clean it up. now I don't know how much was taken off before. Now mocking up the short block I have .078 piston to deck measurement. Is that safe? Being .040 over what head gasket should I use? Thanks for any help.

wow that's a long way down they must have used cheap 77 newyorker cast pistons.
Use the thinest shim (steel) gaskets you can get. what heads and cam but sounds like a 9 to 1 engine .

however, I would change the pistons to get as close to .010-.015" in the hole. good quench is essential on a 440. and after cutting the blocks deck ,you need to check the valve train geo.

I have 906 heads and a .488 lift the pistons are a flat top with no valve releves .

Also must check your intake manifold for alignment with the heads after machining an unknown amount off the block.

nuther good reason to can the pistons.....

OK tossing out the pistons what should I go with?

Well you will have no valve clearance issues.
will run fine in my opinion.
With a steel shin .020 to .022 gasket you will have about 9.3 to 1 or a tad less and poor quench. If you were to use a composition .039 gasket about 8.9 to 1 and worse quench. you will be fine but things could be a way better with a 0 deck or closer to 0 deck piston.
would be nice to know what was taken off before I would have the deck height measured and go from there.
The machine shop can measure it if they are any good at all.

You have to know the deck height of that block and the CC of those heads would be nice too!
Lots of piston options available but that means a re balance too and maybe new rings if you go 1/16 1/16 3/16 if you are at 5/64 5/64 3/16 now?

Could I cut the heads down? Would that help?

well it helps compression and quench a bit as they are a non quench head anyway.

What's your plans for the motor? A 9:1 comp 440 can/will fry the tires on a street car & no worries about today's crap fuel. Should be able to make 450hp easily.

Engine is going in a 70 fury with a six pack set up street car all day, lots of hwy driving

First I'd plug the specs into Kieth Blacks calculator to see what SCR you have. Maybe .022" for the steel shim gaskets and a guesstimate on the head CC's (what heads?). since you are torn down it'd be a good move to go with some higher CR pistons as mentioned if that is in the budget but that MAY require rehoning to get the wall clearance/finish correct (I'm assuming from what I read that it was built then not run?) and you MAY need to rebalance with new pistons. Be SURE & get the correct cam in there to build some Compression. Steel shim gaskets with alum paint will work most of the time IF the heads/decks are flat & you said your decks are. You'd wanna set the heads & gaskets on & LIGHTLY snugged with several bolts then see what the intake alignment is & mill the heads' intake surfaces as needed.

The Speed Pro forged six pak pistons with 4 valve reliefs work very well on most rebuilds I've used them on several builds pump gas street motors and ended up with 9.2 to 1 to 9.7 to 1 compression ratio with blueprinted blocks and 906 and 346 heads cut to make the correct CC to get the compression ratio I wanted All of those motors,three of them, made 500+ HP and 540+ Ft lbs on CA pump swill back before 2005 with both the Performer RPM and Mopar M1 single plane 4150 intake intakes and a BG Speed Demon 850 CFM carb