I don't think that actual number exists, but if you google it there are forums which say 82 (see below which I got from another site). Out of the 82, some may have been equipped with a 440 6 pack but it doesn't break that down. That said, I do know that a sun roof (factory one) was added to more than one car over the years so if this is an issue of valuation you would need to ensure it is a factory installed roof.
This is from the other site
The 1970 production printout from Daimler/Chrysler says .2% of the Challenger series that year had sunroofs. I don't have the figures from them for any other year but Galen's book has these figures: 1 T/A, 114 Challengers and 82 R/T's had sunroofs for a total of 197 in 1970. 21 Challengers and 27 R/T's were so blessed in 1971 for a total of 48. His 1972 figures do not show how many sunroof cars were made, but between 1970 and 1971, there were only 245 of them built - a pretty rare feature.