The hobby store was more into aircraft, but they sold parts at full retail by the sound of it... Retail I have found them online for the same, but eBay much less... (.15 harder to find, looking to retrofit to a .18 if possible)

I have to do some research when I get time to look at the buggy again... But when I do, I will post my measurements. I know exactly the engine you have with the black head, as many others seem to have gotten that one as well...
If your carb will fit, I may buy it, unless I find a good deal on an OS on eBay, since I hear they are a much superior product...
Do you even have your Smartech anymore? Just curious... Pretty sure you got a better machine since, right?