help remove crank pulley '86 B2000

Definitely the easiest solution.

I have never had success by putting the truck in gear since the springs in the clutch disc create a cushion.

You could possibly have success by cranking the starter ( I have had mixed results) - make sure you pull the coil wire off FIRST.

I've been happy with my $50 Harbor Freight 1/2 inch electric impact wrench for the last dozen years (I don't have room for a real compressor). For me, I'd try that.

Incorrect, the size is 21mm, it's a metric bolt.

Yes, it is 21mm, if you have to use a STD it is 13/16

7/8 is 22mm