Am going to do some measurements over the weekend sometime. I think its designed a little better than some of the earlier stuff with the drive through stays.
As for the groupset, I would imagine that it would be a replacement - or is it? Late build frame, brand new Deore for the '87 model year making the Suntour look a little out of place? Couldnt say. The previous owner said that he'd bought it second hand from the original owner who had 'upgraded' the spec at some point.
I could go mad and make it a catalog correct super perfect build but I just dont have the patience or frankly the budget. I do have a good start though. Mavic Oxygen M6 rims, full Deore MT60 (if I ever source a bloody left hand crank arm!)