Looking For 225 Oil Filter Adapter Double Side Thread
I thought the /6 had a long check valve in place of that fitting.
Initial production had just the male/male thread adapter (№ 1739 619).
In '61 a standpipe was added to the adapter (adapter/standpipe assembly № 2268 966).
In June '62 a check valve was added (adapter/check valve/stand pipe assembly № 2402 607).
For '73 the standpipe was shortened to accommodate the shorty filter Chrysler standardised on in production. This shorter standpipe/check valve/adapter assembly № 3577 848 was used through to the end of Slant-6 production.
Most all aftermarket oil pumps have come with just the adapter, no standpipe or check valve (back to № 1739 619).
The standpipe helps keep oil from draining down out the filter after shutdown. The check valve helps even more, though it does add some restriction to the flow of oil. If you can't find a standpipe, there are heavy-duty oil filters available with a built-in standpipe (not the same as the antidrainback valve, which they also all have). Wix 51806, NAPA Gold 1806, Purolator L30137, Baldwin BT216.
Seems to me there might be a market for someone to machine new low-restriction adapters with standpipes. I think Doug Dutra used to do this.