Maybe you know all this already but thats a prety good brand of offset kart chassis made for (left turn only) dirt/paved oval racing. You'll probably find its frames design will make it turn left
really-really well, but it most likely wont turn nearly as well on the right hand corners.
I'd guess thats an older model but I'd think a brand new Specter rolling chassis would cost more like around $1500 or possibly more. (and thats without a motor, tires or usualy a seat)
Here's a link to the Spector kart website:
http://www.specterchassis.com/
You'll find quite a bit of Specter oval race kart info posted if your do a search over on Bobs 4 cycle forum, but I doubt you'll find anyone that ever converted one of these offset chassis karts to a shifter. Shifter karts usualy race on paved road courses and they use the more conventional, straight rail type sprint-kart frames that are designed to turn both right and left equaly well.
If its a 2005 or newer model and the frame hasn't been damaged/tweeked/bent, I'm thinking It could possibly be worth as much as $500 or more to some oval kart racers.
(edit: I'm thinking
this seller would accept an offer somewhere in the $150 to $300 range, try offering him $150 to start)