Town & Country / Pioneer DEH P5500MP

I have a Pioneer DEG P5500MP that was in a 1996 Dodge Caravan. The car was hit and totaled but I took out the stereo. Now, I have a 2000 Chrysler Town and Country and I'd like to install it there. I figured out how to get the dash grill off and got the old (factory) stereo / tape player out. The wiring adapter from the Caravan seems to be right for this car but there are two wires that were attached to the old stereo that don't have a place to connect on this one. One of those appears to be the ground -- it's a bare wire strap with a largish eye at the end and it was bolted to the back of the stereo case. There is no hole in the Pioneer that will fit that bolt. The other wire is a smaller one that clipped onto a piece of what also appears to be the stereo case (metal). In this case, as well, there is no obvious way to connect that to the Pioneer. Are they both ground? Do they both need to be connected?

There is also one loose wire coming out of the wiring adapter from the Pioneer that's not fed into the connecter. It's a black wire and has a horseshoe shaped tip. I assume that's supposed to be connected to ground.

When I attach the two ISO connectors to those in the car, the stereo doesn't come on, which makes sense as long as the unit isn't grounded but when I hold the black wire from the stereo to the wire strap (I gripped them tightly together with vise-grips), it still doesn't come on.

I suspect the solution will be simple but I'm not seeing it. Any advice would be appreciated.