Originally Posted by 68NovaSS
The do share the same bore, but not the same stroke. The 283 stroke is 3.00", the 307 is 3.25".
I'll give you a start in your search, the 740P piston was manufactured by Ohio Piston & Pin, now out of business, and sold under the brand names Nytel and Ertel. They were once associated with Dynagear, but not sure in what capacity.
Maybe some here from back in the day can shed more light.
According to the Badger Pistons website:
July 2008 – Badger Pistons, LLC relocated its operation and warehouse to Bedford Park, Illinois.
May 2006 - Badger Pistons, LLC relocated its manufacturing operation and main warehouse from New Albany, Mississippi to Marinette, Wisconsin.
February 2003 - Badger Pistons, LLC was formed with the acquisition of the piston manufacturing plant and the remaining piston inventory of Dynagear Corporation.
1998 - Dynagear Corporation acquired Ertel Manufacturing Company. Shortly thereafter, all piston production was consolidated at the New Albany, Mississippi location.
I have to wonder whether 72chevy's engine is in fact an original 327 or a 307 overbored .125". Can a 307 be safely bored .125"? No matter, if it's using a 740P piston it must be a 327. If it is in fact an original 307 with a .125" overbore I would be very leary of doing any further overbore for this build.
Cobalt327 made a good suggestion to run the compression ratio figures. I ran the compression ratio using 4" bore, 3.25" stroke, 5.7" rod, standard .025" deck height, a .015" thick by 4.1" bore head gasket (Fel Pro #1094), 7cc for piston dish (flat top with 4 valve reliefs), and 64cc heads (the double hump heads). I got a static compression ratio of 9.43. Using the specs for a Comp Cams 260H I got a dynamic CR of 7.99 so your build is well within range for pump gas use.