I replaced the split charging solenoid for my dual batteries. I forgot it was in gear and went to start iy. It lurched heavily. Now it won't do anything. No clicks and certainly no attempt to crank. There is a voltage drop, but that's it. Did I fry my starter with just one turn of the key?

Doubt you fried it but you could have jammed it in gear. Try putting it in gear say 3rd high with ignition off and rock the truck back and fore. Given it's a Landy you may need a couple of mates to help do this.