Boy, did I screw the pooch

So @wasteddays , what exactly do you disagree with? That a picture would help show us where the OP is having issues? Or that a 90° filter isn't needed with Dougs's D453's if you use the right oil filter?

Because pictures always help, and I've been running Doug's D453's with no 90° adaptor on my 340 with a Canton oil plate and a K&N PS2004 for many years now, it fits great. And the Canton oil plate is actually thicker than a factory oil plate, so that actually reduces the header clearance further.