The groom's attire was a no brainer for us and isn't exactly rockabilly, but may give a few of you reenactor types ideas. My fiancee is really into Indiana Jones and has quite a bit of his clothing already so he decided to dress like Indy in the beginning of Temple of Doom.
All he needed was the white tux jacket which we found on e-bay for $40, including shipping. It was a little bit hard to find because it has a peak lapel, as opposed to the more common shawl lapel. There is also an ongoing argument as to whether or not his lapels are satin or matte. After viewing a bunch of pictures and watching the movie, we came to the conclusion that they are slightly shiny, however the jacket we found has matte lapels but for the price we weren't going to complain.
For the groomsmen we had originally thought about bowling shirts and dark pants or jeans. We quickly decided to change to cuban cigar shirts or guayaberas in different colors and black dress pants because it would be a bit more dressy and match my fiancee's tux more. Instead of flower corsages the guys will have either a white or red handkerchief, depending on which color better matches the color of their shirt. We found all 5 shirts on ebay and were able to get them for less than $18 each. There is one shop in particular (Goodfellas Wear) that has them arranged by size, which makes is SO much easier to shop. The guayaberas in this shop are basic one color shirts, which can really work if you want the same color for all. If you want fancier ones (like the one pictured) you'll need to search ebay a little bit more.
As far as shoes, we are getting married right on the lanes in the bowling alley and we need to put something down so we don't wreck the finish of the lanes. To save some money and headaches we are having our bridal party wear bowling shoes during the ceremony. I, my fiancee, and our officiant will wear regular shoes and we'll probably get carpet runners to put down in a T formation.