G'Day Terry, The K8 engine is a good unit for sure, and sad to say not as fragile as my F2 engine either. Don't pull it apart though, I would rather buy an engine in one piece that I can crank over with the kickstart pedal to check the compression (and hopefully not have to rebuild) than one in pieces.
The engine in my K3 is a good K6 item I bought at a swap meet for 150 bucks. It had a badly repaired alternator cover but otherwise looked ok so I just tidied it up with some good covers etc, fitted a Dyna S ignition, rebuilt and bench synched the carbs, did the valve clearances, and just stuck it in the bike, and it runs sweeeeeet.
Pricewise, how long is a piece of string? Basically, it's what you're prepared to pay on the day. The guy at the swap meet had lugged it around to a couple of swap meets and was surprised that no-one was all that interested. He'd been writing the price on the valve cover, then crossing it off and writing a lower price as desperation took hold.
He'd started at 350 and by the time I saw it on the Sunday as he was about to pack it back into his truck it was down to 150 and I felt sorry for him and didn't bother to haggle. I often see good complete engines go for only a hundred bucks or so on ebay, which I find incredible seeing that people will pay that or more for a good pair of sidecovers! If you don't need to unload it, keep it Terry, it's full of very expensive spare parts! Cheers, Terry.