68 Z/28 EXHAUST MANIFOLD OUTLET FLANGE BOLTS

[pjbizjak]

I have a 68 Z/28 04A build and I want to know what type/size bolts were used to connect the exhaust pipe to the exhaust header outlet flange? My left side manifold (3872683 dated C18) has I believe are 3/8 coarse thread bolts, both going into the manifold and for attaching exhaust pipe. My right side manifold (3872730 dated D18) has, again I believe,  3/8 coarse thread going into the manifold but fine thread to attach exhaust pipe. Any known reason for this except that the right side has the heat riser?

[JohnZ]

Exhaust manifold flange studs and nuts were 3/8"-16 thread; if you found studs with 3/8"-24 (fine) threads, someone replaced the originals with the wrong studs.