Dakotashooter2,
My first press for shotshells was a Mec 600 JR. I bought it in 20 Gauge initially and then later decided to get one of the kits for 12 Gauge. After all the time it took me to set it up for 12 gauge, I went down and bought a second MEC 600JR. in 20 Gauge and decided never to try and switch them again.
That being said, if you REALLY want to do it, try The Graf & Sons Catalog.
Their part number for the .410 conversion is MEC8335410...$44.50.
Or...www.grafs.com or...800-531-2666
Take Care,
Ka6otm