A little useless info - the Henry J engines are Willys engines, not Continental like the Kaisers and Frazers are (except of course the Darrin which also has a Willys mill). If I was within driving distance I would probably take you up on the six.
If you don't get any takers here on the four, you may want to post it on the one of the Willys Jeep sites as the Jeeps used that engine for many years and the Jeep crowd seems to be more interested in the 4.
Do you have any other Henry J parts?
There are a couple of things I'm looking for.