WIW: RB "906" heads

I have a couple sets of big block 906 heads im taking to the swap meet in october. I dont have much experience with big block stuff and would like to know what they are worth. Original heads off engines that will need to be redone. So what are core 906 heads bringing these days?
I also have a pair of "902" heads.
Are stock 440 intakes worth anything?

what’s the letter in the casting on the bottom of the head?