The C8 and D2 heads are the same. Just the D2's had hardened seats from the factory. Both C8 and D2 have 68-71 cc chambers. The C5, C6 and C7 71-74 cc chambers. The AIR or thermactor tubes are a smog related item and you don't need them. I'd ask if these heads have hardened seats installed besides the D2's which have them stock. Try the place Tech mentioned also. They might be able to hook you up possibly.

G.