[427king]

I believe that one is factory done,not altered later. The open plenums were made from both the 2 and 3 hole plenum intakes. The 2 hole were modified to leave an inch or so of the ribbing of the plenum in the front and back of the intake,while factory 3 hole intakes were modified exactly as you show above,as it was the only way to open the plenum on those . The 069 and 093 were the same intake and many times both casting #s were on the same intake. Other times the 093 was cast over the 069,as in the early L88s. All the 66 dated 093s ive ever had were open plenum identical to yours.The later 198 intakes all had the open plenum[with the 1 inch partial plenum in the front and rear]