One thing to be cautious of - it's real easy to make an old Farmall look great with just a few bucks worth of bright red paint and a new decal kit. It may look great but be hiding serious problems. When the seller says restored - just how much was actually gone over - and does he have receipts/pictures/anything to give you a sense of how much, and how well, any such work was done? Make sure you get a chance to start it from cold - and run it until it's fully up to temperature. Look for signs of welds under that paint anywhere they seem out of place - including as much of the engine, tranny/"tube", and axles as you can. Around here, $2500 would be a more than fair price for an A/Super A/100 that is in decent shape - cosmetically and mechanically. They can go quite a bit higher for really nice examples. Very popular.