The C6-G intake is a 66 390 GT item. Hopefully the rest of the engine is also. A nice engine with 335 hp and 427 tq in stock trim. The block casting numbers are probably generic meaning the same numbers were used on different bore blocks. The heads however can be ID'd by that number between the plugs. Date codes off block and heads will help also but you'll have to remove the valve covers for the heads and crawl underneath for the block. You can measure the stroke through a spark plugs hole. I can fill you in depending on how far into it you want to dig. G.