intake/exhaust mounting, what am I missing?

3/8 center stud first appeared in the 1973 Chrysler parts catalog part number 152568.
Exhaust and intake manifolds changed in 73 to accommodate the newer size fastener.
This was covered by Doc (Doug Dutra) way back in January 2010 over at Slantsix.org
Chrysler was having problems with the thin triangle washers #2206416 as seen in the 1972 TSB chapter 11.
You can find this at Hamtramck Registry.
Evidently the TSB solution was to time consuming so new thicker washers were released.
A manifold fastener package was available in 1973 that included all the thicker washers: #3744826.