factory ‘new’ 400

I came across a “Factory New” 400 short block w/ flat top pistons .100 down in the bore. He sold me that and a fresh set of 346 heads assembled for a grand. At that price I couldn’t pass it up. I’m guessing compression to be around 9 to 1 w/ this combo, using a thin head gasket. The thing that I thought was strange, is the flat top pistons .100 down. I thought everything by 77 was 8.2 to 1 (advertised) And you were lucky if you really had 8.0 to 1 compression. Any thoughts? The “New Factory Built Eng.” tag has the part no. as “5 06″

I came across a "Factory New" 400 short block w/ flat top pistons .100 down in the bore. He sold me that and a fresh set of 346 heads assembled for a grand. At that price I couldn't pass it up. I'm guessing compression to be around 9 to 1 w/ this combo, using a thin head gasket. The thing that I thought was strange, is the flat top pistons .100 down. I thought everything by 77 was 8.2 to 1 (advertised) And you were lucky if you really had 8.0 to 1 compression. Any thoughts? The "New Factory Built Eng." tag has the part no. as "5 06"