Alpine Issues

I'm putting an Alpine CDE-102L in a 1991 b2200. I put both diagrams next to each other and matched the wires exactly. but what's throwing me off is the ground wire. It says "chassis" on the diagram, but if I have to ground it on the truck then where's the original ground from the stock wiring? And when I did ground it out on the truck still nothing will turn on. I'm also unable to find a wiring harness for this year. SOMEBODY PLEASE HELP!
Thanks

metra part #
70-1781 for future reference
This is the part number and brand that should keep you from cutting the factory harness off. all you have to do is wire it to the aftermarket radio your installing and plug it in. much simpler and you wont have to trace(test) any wires or look online for a diagram.

on the truck side, there is no ground, the factory radio used the all the metal brackets that it was fastened with as a ground, with the alpine radio take the ground wire and attach it to a clean spot of steel in the stereo console area

Yep the factory radio is grounded to the chassis, I grounded my aftermarket radio to the bracket mounted on the trans tunnel just make sure its a clean bare metal spot.