radio wiring question

i have an 87 ram 50 and i went to install the new deck but saw that the original wiring is only four wires. Black-GROUND,Red-POWER,Green-SPEAKER(+),Blue-SPEAKER(+). the issue is that aftermarket radios obviously have two wires for each speaker (+) and (-) and the original harness only has the positive. I guess my question is do i ground the speaker with the black radio ground? or shoud i ground them on my own to a good ground that i have to find? other idea was just new wires for each speaker two straight to the deck, also as far as power do i put the red(switched power from deck)and yellow(constant power from deck) straight to the red and splice all three together?

side fact this truck is amazing its an 87 with 68k,5 speed and no rust just awesome i love the gem i found.

I always just ran completely new wires when installing any stereo stuff. I'm not using any of the factory wiring or speakers at all. Just run the yellow wire to a constant power source and the red to a switched (ignition) power source. As for the speakers I'd just run new wiring.

Just forget about using the factory wiring harness all together except for a power source when installing an aftermaket stereo head unit.The red wire from stereo needs to be connected to a source +12volt at either the fuse block or out of the factory wiring harness that can be tested with a test light that looks like a doctor's shot with a wire on the back with a gator clip for ground.This connection will be hot only when the ignition key is in accessory. The test light will go on and off with the turn of the ignition key. The yellow wire from stereo is the "memory keep alive"(so you don't lose time?preset radio stations) and needs to be connected to a +12volt always or constant on source either at the fuse block or in the wiring harness for the radio. The test light will light up regardless of key position. The black wire from stereo should be grounded at the chassis or any metal part of the body. DO NOT ground speaker wires to this same ground it will fry the stereo. Run speaker wire to your speakers from the supplied speaker wire connections from stereo Left+ Left- Right+ Right - and do the same for front and rear if four channels are used. I installed a JVC head unit in my 1990 Mighty Max without any problems so, you shouldn't have any either if you just follw the steps I mentioned here.
GOOD LUCK to Ya!
Scotty D

^^^^^ thats what I did also