What designated the "swept" rear wheel cut-outs, I see some with a fender-skirt to make it look that way and others it looks factory as if it is a 56' model?

 

Here's the '55 Brochure that shows various skirts. Hope this helps. Looks like 98 had the swept cut outs and the other models offered skirts to add that look.

http://www.lov2xlr8.no/brochures/olds/ol55/ol55.html

 

I have a 55' 98 and it has the swept add on fender skirts, and my 2 super 88 parts cars have the same, I was looking at different models online and it looks like the "Holidays" have the built in swept cut-outs, never paid much attention to it until I had one!!

 

Good job!! If you look closely at the brochure ^^^^ they do show the 98 four door sedan with the fender skirts. Just like the one you have (I looked at the pictures in your previous post).

How 'bout that. Learn something every day.......