Chrysler started using a shorter oil filter in '73 because some V8 installations didn't have room for the longer one. They decided to just use the shorter filter even in applications like the Slant-6 where the longer filter still fit fine. The NAPA catalogue just knows what's been programmed into it, which is the original-equivalent filter; it does not know what else will fit and work.
If your oil pump just has the stubby oil filter thread spud, without a standpipe 2-3" long sticking up from it, and you want to make extra-sure the engine gets oil immediately on startup, you can use the № 1806 filter. Same as 1515, but with inbuolt standpipe.