Try the Prothane Isolators
The Prothane spring isolators are really for an IRS Cobra. I got mine at:
Laurel Mountain Mustang
You'll need Flash Player to access the site (hate it!). Once you're there, it's under
"Late Model" then
"Chassis Components" "Prothane & Polyurethane Bushings". Near the bottom of the chart is
"1999-04 Cobra IRS Coil Spring Insulators 6-1709BL" The price is per pair, so you'll need 2 sets. The Cobra only uses them on the LCA, but an MN-12 uses an upper and a lower for each side, which are the same size. I've ordered from them a few times with no problems.
I'll try to post a pic later tonight (need batteries)... I've had the isolators for quite a while, but just got new springs today. Just checked - they definitely DO fit.
Best of Luck!
That is all...