Being of close scottish heritage,    before I scrapped out that engine I
would run a cylinder hone down the bores, especially the offending bore.      
If it cleaned up, I would pop in a new set of rings, maybe a new set of big
end bearings and re-assemble the engine.   I would also check very carefully
the piston in that particular bore.
I have done this very same thing on a VW diesel pick-up and solved a badly
smoking engine problem for about $120 and a days work.    Its still running
fine, in someone elses hands 4 years later.
I admit a big difference is that I could do all that without removing the
engine from the vehicle.
Good luck,
Steve Cotsford,
'84 Westy