Thermostat Housing sizes

Chrysler used two different size thermostat housings for V-8 engines , also called water outlet connectors.
The larger size was used thru 1978.
The smaller size was used from 1979 and later.
3698565 - 1978 and earlier
4100490 - 1979 and later
Examples can be found on eBay
Part number search on rockauto shows aftermarket housings.