383...diff. year question...

383 "Stock Piston Depth"

68-69 383hp had positive deck height. Actually I thought the 70 and 71 383 hp engines did also but maybe not. 68-69 hp used the 906 heads. I don't remember if the 70 and 71 did are not.
Ok, thanks. How did they do that? Did the '68-up block have lower deck heights from the factory?