Are you using the TTI 636A headers? Those are the ones that fit the early A's with a small block. Use the factory 90* filter adapter and cut the mounting nut like what's in the directions (the footnotes). You can read the directions on line from the TTI website. I've got them on my '66 Valiant, if you follow the directions they fit (barely, it's a tight fit). On my car, I just loosen the filter a little, slip a zip-loc baggie over it, unscrew the filter by hand and pull it up out of the engine bay and it's done. No oil is spilled. You don't have to crawl under the car, changing the filter is done from above. Easy deal. Finding a 90* factory adapter should be too hard, it's a very common and easy to find part.
Russ.