Tell the guy to take it or leave it. He may sense you don't know much about what you're selling and is trying to squeeze your price down.
Re. 3100 vs 3600
3100's are very prevalent in the antique world where the 3600 is more rare. The long wheelbase of the 3600 provides a bit smoother ride on a bumpy road and you can lay a sheet of plywood out on the bed.
It's all about personal tastes...
