NIce post.... You can TEMPORARILY use the throttle cable adjustments on the new carb caps to set the idle, but....you're asking for problems if you do. Turning can cause the R's to rise, and you may never get a steady set idle from both carbs. You really need the brass screws to do that, and keep a tad bit of slack in the cable....
I think I still have a brand new (2 or 3 rides on it) twist throttle in my garage. I know I took pics of it to send off, but I don't remember if the guy actually bought it or not. It's a Motion Pro CR style twist.
Yes, you'd still need the cable, tops, drill, tap and brass screws...
Check out Vito's Performance....they sell parts individually....
I"m not sure where you're getting 80 just for the carb caps. For 60, you get EVERYTHING here, except a twist throttle...(and, if you do go twist, you'll need a different cable)
http://www.magicracing.com/TORS-Eliminatio..._p_310-731.html