There were three six cylinder engines that were "Kaiser" engines. The 226 CID which was used in the Kaiser and Frazer cars and the 161 CID flathead (or L head) that was used in the Henry J deluxe models and the 161 F head that was used in the Darrin sports car. The F-head had the intake valves in the head and the exhaust valves in the block so that would not be the one you described. On the 226 and 161 L-head engines, the intake and exhaust manifolds bolt together as you point out. On the 226, the manifolds have very round corners. On the 161, the intake has square corners and is more rectangular in shape as opposed the round shape as that of the 226. The 161 was the first engine to have a PCV valve. The PCV valve screwed into the intake section just below the carb. The 226 does not have that.
Hope this helps. If I get chance over Christmas, I'll take some photos (the cars are in storage about 20 miles from me) and post them on here.