Mmm...that makes a lot of sense, and answers that questions completely. Thanks! I'll take a look around to see if I can find a full K top end in good shape to swap on.
Now in terms of the guides, is this also something I could do on my own? I'd take it to a shop to get the guides honed and the seats recut (if you guys suggest it), but the actual guide replacement is something I'd be willing to do if it's possible. I do have a fair bit of experience with rebuilding british engines and small turbo car engines on my own, but I've never dealt with guides before.