Well I totaly understand about keeping the car "original", and having that "warm and fuzzy" feeling of buying the parts from callaway, as I did just that.... My advice is in retrospect, and I learned the retrospect when Callaway let me down in many ways that I wont get into here.
I know these cars quite well, in fact very well.... Fact is that if you brought me a B2K with a Backyard Billy-Bob Built wonderbar, I could not tell you if it is a callaway part or not if it was done nice. I say this because I have two wonderbars from callaway... Neither look exactly the same, but do the same job. They also have no "majic" mark or code on them.
If you want to buy it because you want callaway to enter some information on your car into their database, so 20 years from now, your prospective buyer will call them up... (if, if and only if they are around and willing to give out this info) and have Callaway tell they that they got a wonderbar... Thats great, but thin.... real thin, and do you think that is really going to be a deal breaker if these cars come back strong one day???? I doubt it...
If these cars say "B2K" thats all that matters along with the fact the car is in nice condition with and decent milage. Having the car original is great. If you have a 100-5000 mile car, I would not touch it in any way, nor would I risk the car to be sent off to callaway for any reason.... In fact I would take the wheels off the car and all the fluids out, jack it up and seal it up for a better day, as today is not that. ... Its GTO, Chevelle, 442 and mid-year Day......
If you have a nice callaway, and as long as you dont get stupid with it, you will be just fine with little things like this, and the wonderbar is not stupid, even if its built by Willie the Welder.
If you got the money and dont mind letting go of it, get yours from callaway on this deal! . If you dont know how to work on cars.... Send the car to Callaway along with a blank check or CC and expect about 2K more to do it. If you cant afford to do this and do not know how to work on the car and do not know someone who really understands the car 100% to do it for you.... DO NOT EVEN DO IT!
Installing a wonderbar is not that difficult, but its not as easy as you may think. If you are a good wrench and want to save some cash.... Modify yours... I can attest that the work is not much more than buying the thing from callaway, reshaping lots of it and putting it on.