Did you ever find your LWB conversin kit? I actually purchased the LWB kit when I bought my R40 new in 2003 (or thereabouts -- it's the blue R40, the second to last year they made it). I have the (blue) boom, steering linkage, stem, bar, riser, maybe even the cable guides custom cut to the riser. I bought my bike in the USS/SWB configuration, and have always preferred that.
I have never installed any of these parts, except to take pictures when my wife sold her R40. I have not tried to sell it and haven't really researched the value, but you are welcome to PM me with an offer.
Along these lines, I have a Vision R40 that is long wheelbase right now. I tried to convert it "back" to a short wheelbase, but encountered a problem. Now when I turn the handlebar to the right, the front brakes squeeze down. Also, when I turn to the left, the brakes are too loose to actually clamp down. I read somewhere that I had to lengthen the cable, but I don't see how that would help. Have any of you encountered this issue or know anything about it?