I just ran across this post. Brand new here, but a long term Willys Overland Knight Registry Member.
I am very familiar with sleeve valve engines from Willys Overland line of products. I own a '27 Willys Knight 70A cabriolet Coupe. In addition I own the one and only known 1933 Willys Model 8-88A. This car has been registered to the W.O.K.R. consistently since 1975 and I am currently the 5th owner. The Willys 8-88 was 1932 year model and there are currently about half dozen known, so still extremely rare. My 8-88A is currently under restoration.
The model 66E Willys Knight was a single year production as was the Willys 8-88A. The two vehicles were literally identical with the exception of Willys Knight having the double sleeve valve 6 cylinder 87 HP engine while the Willys had a flathead straight 8 rated at 80 HP. The only other difference was badging and a slightly different radiator shell insert grill.
Attached pics are of 1933 Willys Knight 66E (brown car) and 1933 Willys 8-88A Black and white pics