Welcome.
That's a posh one, innit.
Depending on where you are, have a chat with Des at Pegasus (nr Sittingbourne), but not this weekend because he should be hard at work on my clutch ;) Good bloke, knows his stuff, and does excellent work.
Because they're the questions you should be answering in your ad, if you want it to get any attention.
Don't care if it sells? Don't complain that no-one's responding.
Never found fault with my Goodyear Wrangler AT/S. Perfect for the usage you described, and reasonably priced. The one that tore would've tore if it was anything else - huge razor-sharp flint sticking out of a verge.
No-one else use them?
They spilled gear oil in the cab, which caused the gearbox to asplode, drenching a small mouse who, terrified, sheltered the dash, and is now running a tiny gear oil factory. This is what you're smelling. Feed it.
Suspect bent shaft next then.
By the way, you can't just pull a bolt and replace it - there's a tightening sequence and torque values.
You'll also want to see to its seats and seals.
Presume rocker shaft is present and correct? Clearances good? Valves valves and not just aimless flappy-up-and-downy-bits (suspect one or more of these and/or its connect-to-the-rest-of-it-bits has gone "a bit off")?
Oh yes, right you are.
Well, I have my idle turned down a little because I like it to sound like there's a team of belligerent retired blacksmiths hammering out raw hot grunt under the bonnet. This does not imply that any favours are being done for actual workings.
In the absence of a timing...