I'm pretty sure that is an '87. It has the look of an '86 from the bars, but I think it's an 87 because: the bottle cage bosses are further down the down tube, it has 87 correct parts (stem, 983 cantis, logo'd hubs). The shifters are 86 spec suntour LD4700s but they are good. The bar is not original as the riser on an '86 is 22.2mm clamp dia. Your stem means the bar is aftermarket ('86 models had a 4 bolt faceplate bmx like Win stem).
Does it have paw print pantographs at the top of the seat stays? They appeared on 87 frames.
You can get repro Bullmoose bars from PX, I think there are two types. Be aware new ones dont have cable stops. They sometimes come up on eBay, I had a saved search on eBay for a couple of years, and specifically wanted an original 80s Nitto one, and didnt think twice when one did come up. There are a couple for sale in the states at the mo if you could stomach that?
Ps think you're right 're mixte option, but even they had differences to the regular bikes. My old dear had one from new also but sadly sold it some 10 years ago.