Can anyone figure out what compression would calculate to with pistons I found for 426 hemi. Would be appreciated. Thanks

Bore 4.375
Stroke 4.15
Deck height 10.720
Piston comp height 1.665
Effective volume 82.1cc
Rod 6.860
Head stock 174 cc
Head gasket thickness ???

Diamond has a good online calculator.

You'll need piston dome cc.

Would also recommend measuring the combustion chambers if you want to be accurate as "stock" isn't always the same.

Agreed there are many on-line calcs but you'd need to know how much positive CC the net volume is on the piston to be somewhat accurate without mocking it all up and doing the measurements. You may be able to find that looking up the piston on-line but again it will only give you a general idea.