Tandem Cycling - Help identify this tandem?

I just got this tandem which has obviously been Frankensteined quite a bit. A restoration is probably out of the question, but I'd like to get it back on the road in an appropriate style. I'm mainly wondering what style of handlebars it would have had, since the originals are missing. There are two rivets in the head tube where the badge used to be, but no stamps at all, either under the bottom brackets or on the dropouts. Any decals are under several layers of spray paint:

http://www.donrogerson.com/images/tandem/IMG_5533.jpg

This frame geometry looks like some Schwinns from the 50's, but the triangle is different - this one has forked tubes. As you can see, someone stuck a pair of BMX handlebars on it, and also jerry-rigged a shimano 3-speed hub for the rear wheel. The fork does not seem to match - not enough rake for the probable age of the bike. Probably came with the BMX bars. There's an idler, but this appears to have been improvised using a hanger with a channel in it U-bolted to the bottom tube. Right next to it is a hanger with two holes that probably held the original idler.

Here's one of the chainrings - all three match and are certainly original:

http://www.donrogerson.com/images/tandem/IMG_5534.jpg

Another clue, there is a bracket near the rear bottom bracket for one of those built-in kickstands like I've seen on Columbias:

http://www.donrogerson.com/images/tandem/IMG_5536.jpg

Here are the rear dropouts. This blue appears to be the original color:

http://www.donrogerson.com/images/tandem/IMG_5537.jpg

I've been through the photo archives and find nothing exactly like it. If I can't identify it and find an image of its original appearance, I'd like to know a few things before trying to get it in shape:

1. What style handlebars would be appropriate? (And where can I find a stoker stem?)
2. What kind of brakes? There appears to be a band of paint on the triangle where a coaster brake was probably attached once. I suppose with some coordination, a coaster brake would have worked?
3. Any thoughts on the dimensions of the proper fork?

I'm a fairly competent judge of horseflesh when it comes to bikes, and I know this is no marvelous machine. I'd guess it's a 60s Columbia without knowing more. My nine-year-old and I like bike projects, and this one has really excited him.

It might be a tandem built out of two bicycles. Look at all the welds and see if there is a diference in the welding. Picture shows one weld and it is very clean.

I just finished fussing around with a 70s vintage Columbia Twostep. The timing chain adjuster, dropout, chainring, and (I assume) single-piece crank in your pics look very similar to the pieces I worked with. The frame geometry isn't even close. The Columbia I worked on had it's SN stamped on the quill stem. Looks like that piece is missing from yours.

Good luck!

I had thought it might be a chop job at first, too, but the welds are clean and the tubing the same throughout, so I'm sure now it's a stock tandem.

brewer45 - yup, this one is missing the quill stem. It "smells" like a Columbia to me, though. I think I'll use one as a model for putting this one back together.

Digging a little deeper in the internets, I found this:

http://www.vintagebus.com/bikes/tandem1.jpg

A 1960s Columbia - should just trust my gut! I see that the original had twin idlers. The front seat mount and stoker stem appear to be one piece. That might be hard to come up with. I may have to improvise something.

Thanks!