Charlie,
I have a MDR 300-C PRO, the dops I found to be as close as the OEM dops are Polymetric. These dops are a little longer than the MDR but if needed you can shorten, they also have the vee groove. I also use the Polymetric transfer jig opposed to the MDR. Contact Zane via their website http://www.polymetricinc.com
Greg Hays
The Gem Garden
San Marcos CA