Well, you are stressing my foggy memory here, but as I recall, the dash 5 plugs were broader heat range. Frankly, I doubt you would see any difference in engine performance, so long as "reading" the plugs shows the heat range is OK.
One thing to note, since the dash 5 plugs are used for restorations, you might want to pick them up and resell. They bring a fair bit of $ on eBay these days. Just a thought.
Doug
