It should be. Bucket seat cars used that non-adjustable shoulder belt that was tied into the inner roof structure. Although you might not have the anchor for the belt, the inner structure of the roof is likely the same. I say likely because both of my cars had factory buckets and that non adjustable 3 point. But I doubt Ma Mopar made two different inner roof structures. So it shouldn't be a big deal to put anchor in.
XV sells 3 point retractable belts, haven't checked eBay to see if they have any in stock though. But there are a few companies making 3 point retractable belts for mopars. The biggest thing is just having a "drop" from the anchor to get the shoulder belt in the right spot. I have a set of XV's 3 point retractable belts in my Challenger, easy to install and they work great. I got around XV's customer service by using ebay, I know more than a few people have been unhappy with their customer service.