First of all, thanks everyone for there help!
Tim - you even took the time to post here and on Jalopy....thanks!
Oldcarmark - you beat me to my response: that although it certainly may be the wrong part, it's what NAPA is showing for a '55 Ford. That in and of itself still wouldn't haven't sold me on it being the right part, necessarily. However the MACs catalog is showing the same darn part....a 3 male prong flasher. So that kind of told me that it was the 'right' part, but of course not just like the original.
If I can get the adapters that Tim refered to easily enough, than at least that takes care of the hole wiring issue. Then the only problem becomes not knowing what prongs on the NAPA flasher to connect to the two wires that I have. Anyone have any ideas on that one? 
EDIT: To heck with it....I just went ahead and purchased that IDEAL Flasher you referred me to mark. Thanks for looking that up for me! I'd still be interested in finding out how I would have connected the wires to the P, X, L terminals on this flasher, if anyone happens to know. Just curious at this point, and who knows if someday this will be my only option!!