I never respond to sellers just saying best offer. If they wont put a price on it, neither will I. State a price you wish for and then put "or best offer" or price then negotiable. That way the potential buyer knows whether to ask for a lower bid price or if it is "firm".
My BIL bought a new 6500 Craftsman about 5 years ago for $2500. He takes pretty good care of it, but the deck is getting thin in places just from wear. Depending on condition of mower ( engine, deck and seat) it could go for a High of $500. The LT 1000 will be a bit harder to sell due to the HP and size which would only be for small yards, $200 might be a good price if seat is still good. That mower was about $1000 new, so adjust price accordingly. That AC must be super old as I haven't seen an Allis Chalmers tractor in years (AGCO now). You would be lucky to sell it for $100 but only if it is in running condition.