razorback i didn't catch what model you had but my friends mid 80's 6.9 had to have a constant ran because there were no programable channels and clock. The constant wire powers the radio and memory, the ignition or remote whichever you want to call it just swithes a relay inside the radio to turn it on, the power ant is not needed, if you install an amp just power the remote wire for the amp off of the ignition, the 12v + HAS to be ran to the battery and do yourself a favor and buy a wiring kit if you don't then make sure you put a fuse on the 12v+. The rca cables are simple- R to R and L to L. I have two 12" speakers behind my seat with a 1000 watt amp. I am about to go to one 12 with 1600- 2500 watts- i'm not sure which. Why one instead of two? well you have to match the speakers to the volume of your box, I have 1.75 cu ft of box space and the 12 that i want to go to requires at least 1.5 cu ft of space. Also use an ohm meter to match your ohm ratings on the amp and speakers. don't run maximum power rating to a sub if anything run a little over rms.
I am 18 years old and have been doing audio and video systems since i was 15 I have spent a lot of time reading and listening to audio experts in my area. Only 15 % of the quality of an audio system is the equipment used(head units, speakers, amps) the rest is quality sound proofing, wiring and speaker enclosures. okay i think i'm done ranting but i love audio as much as i love mechanics.
I'm excited man, for once there is something on here that i can give quality info on