This is fairly original judging by the parts you have on the frame and what @
-holiday76 picked up for me.
It was right in between Shimano 6200-series and 6400-series. I have a lot of v1 6400 and the last version of 6200 on the bike. I also have some v0 6400 brake levers that look a lot like 600-ax --- very similar to yours.
Your pedals, crankset, downtube shifters, stem, headset, and brake levers are original to the bike. I would guess that your handlebars, seatpost, and bottom bracket are also original. Obviously, the handlebars would not have been in hobo position.
Your wheels, saddle, and brakes are not original. This was one of Shogun's highest models, so it would not have come with a kickstand.
I would guess that it is from 1986-1988. @
T-Mar might be able to do something with the serial number. I don't think I've ever looked at my serial number, so we can do a comparison.
The Tange 2 is a well made steel, and with the triple triangle, the rear will be stiff. I think it should hold a clydesdale rider at 254# just fine.