My list shows a 4R5 as an 81 XS400H.
It also shows the 81 Heritage Special (XS400SH) as 4R4.
Not sure about the 81's but the 82 Heritage Special had black fenders, forks, brake & clutch levers, foot peg brackets, etc. If yours still has a lot of shiny stuff my guess is that it started out life as an XS400H and the VIN is correct.
Don't forget we are dealing with 30 +/- year old bikes here. Could have been a lot of Bubba's had it before you and some of them may have "Improved" it.