Hi Ant:
On the ERA with a 428FE you CAN INDEED have a sandwich and filter with the "normal" block mounted
oil filter braket. Here is a picture of my old Fram filter (I now use K&N) which is next to the Milodon
oil sump. The filter sits below a Sandwich adaptor and as you can see, the ERA chasis does provide ample room for this setup.
Perhaps on some other Cobra manufacturers' arrangements for the Cobra 427 a chasis member is in the way, but on my ERA (as well as many others) that is not the case. My block mounted
oil filter adaptor comes off the block at the angle of the block and then drops straight down. This is adaptor was provided by Danbury Competition Engines a long time ago back in 1992. I do imagine they are still available.
The fine picture/schematic that COBRA provided shows this setup exactly as I have it.