I have two LKs in .50, loaners for hunts. Bought one new-unfired, for $150 in stainless.
Picked up a second one for $60 with a forgotten load in the bore. The seller fully disclosed that the bore was rusty and corroded, a "parts" only rifle. The interesting part was after pushing the load out, and a few cleaning passes, the bore looks pretty much like new, no pitting, and very clean.
I've converted both with the Knight kits to the 209 red primer. My only advise would be if you find the conversion kit for sale, buy it then.
I found several kits when I first searched, waited a bit, and they had sold out. Took several months to get back in stock.
Numrich has the Williams peep sight for it, here's a link:
http://www.gunpartscorp.com/ad/881050.htm#881140