I wish I'd taken a picture of how I had the weight set in my '89.
From what I've experienced and read, you want weight in the bed. I had 4 concrete hog slats (2 parallel with the tail gate, 2 parallel with the passenger bedside) and then I slid my tool box all the way back against the tail gate.
The tires will spin, but you want them to spin the right amount. It's like getting unstuck from 1/4" of mud or wet grass
When you feel like you're on top of it and aren't accelerating yet still moving, bump it into second.