Regarding fork length: The longer the forks rake out to the front the higher the head tube is off the ground. This difference is very small in comparison and nothing to worry about.
I assume you are thinking of fitting a "Spoiler" complete front assembly on your OCC frame. Seeing as both were made by Schwinn, there's a good chance they'll interchange. See if the steering tube that goes through the bearings on the Spoiler is the same diameter and length as the OCC counter part. If the Spoiler tube is too long you might be able to cut it down and reposition the coil springs. I'm not familiar with how they are secured. If the tube is a diffferent diameter, there are different bearing sets that might work. I can't imagine this swap could not be done, but it sure would be nice to have a Spoiler assembly to measure first.
After I custom make a disc brake mount on mine I saw where someone shared an adapter that would have worked on my OCC forks. Not sure where that post is at the moment.