I don't know if the Dells are more complicated, but they are definitely different - I've never seen them on R65s either - just R90s, even if they weren't the R90"S". Diameter-wise I'm not sure how good a fit they are.
I know that a number of Moto Guzzis used Dells through the 80s also, so a Guzzi rider/Guzzi forum might be helpful in that regard - they are also airheads with dry clutches!
I have seen folks with Mikunis on their bikes - a fairly common cafe' type of change for R75 bikes as well. They can work well if one can get them setup properly, but they also are quite difference from the Bings, so one cannot follow the typical Bing troubleshooting paths.