['ol Pinion head]

Originally, 197's, whether early style with no dates, or the later production style cast in early Dec after the strike, only had 4 holes on the flange area to attach the exhaust manifold. I looked at heads on my '71's engines, as well as extras I have, and pics of both styles that have been on original engines that I've had in previous cars, also pics of ones Ive traded off, all only had 4 bolt holes, not 6.

In the late '80's, there was a fellow from the San Antonio area that at Tx swappers was buying up cracked roundport manifolds and I can remember him telling me, he was providing them to Delfield. Shortly there after Delfield had his version of the A-F body roundport manifolds recast. When he did, he used the later SD manifolds as the model. The SD manifolds have more attaching holes in them. From owning several 71 HO cars & quite a few pairs of 197's, what I believe you are seeing is heads that have had two bolt holes drilled and tapped so typical thin flange headers could more effectively seal. I don't see how a very rigid exhaust manifold, ESP the repro's from RARE, are not going to seal up with the right steel gaskets. Of course, several empty holes with no bolts in them is going to look odd, but some will probably see an oddity of viewing a roundport headed engine in the car. It's your choice how to remedy the problem, it's not like you are in several of our shoes and will get dinked in Concours judging at Nats for having the wrong exhaust manifolds, or get told the oversize manifolds are wrong for the car at Purestock events. just my.02.