The Darrin did use the same running gear as the Henry J so you've checked both boards I see. I will mention that you need to be careful if you're thinking of using a Henry J rearend as there were three different ratios used in the J. The most common one, and the one you likely need for the Darrin, is the 41/9 (4.55:1). This one was used the early four cylinder Js with and without overdrive and the 6 cylinder Js with overdrive.
Then there's the 41/10 (4.10:1) which was used in the 6 cylinder Js without overdrive. Many restorers / rebuilders like to replace the 41/9 with the 41/10; while it is not as quick off the line, the high end cruising is a little better and also, if your overdrive quits working for any reason, you can still do about 60 mph with the 41/10. If the overdrive stops working with the 41/9 rearend, you'll be able to go about 45 mph and the engine screams at 50 mph.
The third type is the 47/11 which was used in '52 - '53 four cylinder Js without overdrive. I've never heard if or how this one might do with 6 cylinder with OD in front of it.
The way to identify which one it is is by a metal tag fastened to one of the rear end cover bolts. The tag will have either 41/10, 41/9 or 47/11 stamped on it.
I see
www.kaiserwillys.com has rearend parts but I don't know if they would work in the Henry J or the Darrin -
http://www.kaiserwillys.com/category/willys-jeep-rear-axle-parts-accessoriesTerry T is the Darrin guy on here. Haven't seen him on here lately but he likely would be able to provide you with good information so check back - this board and the Darrin board.
Also, click on attachment below to see a copy of Rudy Phillip's latest catalog - he may have what you need as well and if it's not listed in the catalog, give him call as he can often point you in the right direction. Good luck and let us know how it goes.
