I took a clay imprint of the dome and cc'd it, I came up with 46cc's. My pistons are definitely .100 down in the bore, my block was a virgin 1966 425 that still had GM bearings. I did remove .015 from each side of the deck to clean it up. I figured compression height by measuring from the flat portion of the piston adjacent to the dome to the top of the wrist pin bore. Then I split the diameter of the pin and added the two. Here's the numbers I got. OEM piston- 1.465 Rebuilders Choice-1.465 Egge-1.410. Adding .500 to these numbers to figure pin bore centerline would put the Egge at 1.910 and OEM at 1.965. Siv-O-Lite lists their 401 pistons at 1.910, Ross at 1.930. Neither of those numbers jive with the measurements that I am getting from a stock piston. If a stock engine has .055 deck clearance and the Egge is .050 down further in the bore then I am right on with my figure of .100 down. Running back to back compression calculations that additional .050 deck clearance drops compression 1 full point from 9.56:1 to 8.43:1. My pistons came directly from Egge and the production date was 2-2013 On a side note the Rebuilders choice piston has the correct compression height but the dome is .070 shorter then stock. The one I measured was .290.