Will dial-a-jets designed for 01 and 02 650 Prairies work on the
03 Prairie with the new filter-airbox?
I know that the dial-a-jets attach to the bottom of the airbox and the guy
at dial-a-jet didnt know about the new filter-airbox and couldn't say
if they would work or not.

Any help would be appreciated.

 

Dial-a-jets mount in the rubber boot on the top of your carbs, which are located inside your air box, under the air filter.

Unless the 03 airbox is a lot different than the 02, I don't see a problem with mounting

One word of caution, you will have to drill and tap holes into your carb bowls for a gas supply, some people don't want to do that.