Fig. 10.14
Fig. 10.15
Fig. 10.16
From 1955 through 1974 all the exhaust manifolds use the same bolt pattern as shown in Fig. 10.14 then in 1975 some of the exhaust manifolds required a Third Exhaust Bolt hole on the end exhaust ports as shown in Fig. 10.15 so if you are swapping heads make sure you have a head which will work with your exhaust manifolds. Also becareful because some of the heads which should have the Third Exhaust Bolt may not have it drilled and tapped as shown in Fig. 10.16. All earlier exhaust manifolds will bolt on to the later heads but some of the later exhaust manifolds will not bolt up to the earlier heads.