I believe 5160 is a common material for this usage.  Youcould go down to the local farm/home/fleet store and inquire about them to get a manufacturers name.

Standen's, McKay Empire
Most larger cultivator companies have their own heat treat facilities.

What's this stuff like to work with? Can it be cut on a bandsaw easily prior to heat treatment?

When I worked for CaseIH I did a lot of the development for the 4300/5800 series of field cultivators. We didn't change the field cultivator shanks much, but the chisel plow shanks were new from the ground up. I don't know what material it was, but I cut a couple of the chisel plow shanks with a band saw no problem. The shank was an edge-on design, so the mounting for the sweep had to be forged to provide the necessary shape and mounting area. While it was hot we also punched two ~5/8" holes for the upper mounting. I doubt they would pay for something too exotic. Obviously you need strength, but you also want some impact toughness and wear resistance.

ISZ