Upgrade my hatch to one with a wiper and defroster. Got a hatch with that from a junkyard recently with that stuff. The hatch is a bit rough but the glass looks good and the wiper motor is there. Will need a rear wiper arm since the one on the hatch is broken off and the switches for the dash. My plan is to transplant those components into my hatch so I don't have to worry about repainting anything. Is the wiring for the defroster and wiper already in the car or will I need that? My car currently has no defroster and no wiper.
I think some of the body wiring is there, but the hatch wiring is not, and you may also need a connector to tap into the fuse panel. It's a standard GM piece, there are three styles of connector that fit battery, ignition, or accessory positions on the fuse panel. The way the defroster connected to power varied between years and models.
The combination switch-light-timer unit for the defroster is rare, and if you have a working one should be disassembled and lubed with silicone grease if you want it to last. You can use the early separate parts style push button and timed relay style, which was also used for Cherokees. A light and momentary switch or button go in the radio pod and the relay just lives in the dash.
Fix my manual mirrors. They barely move if at all. Do they just need oil or are they broken and if so, what parts of the dash will I need to remove to get to them? Are replacements available?
They come apart, but it can be a pain. You need bent screwdrivers and patience. The remote mirrors probably need the cables freed and lubricated as well.
I don't know what would replace them. I've looked around and I was looking at adapting electric mirrors from a Nissan Versa. AMC mirrors come with two different cuts on the stem to compensate for the curve of the door sheet metal. One cut worked on the Pacer/Hornet/Gremlin/Concord/Spirit/Eagle, the other on Javelin and the big cars. I don't know if FSJ mirrors have a similar cut to one of those or not. The small car cut brings the head closer to the glass, the big car cut is further out and varying gasket thicknesses made up small differences from car to car.
Upgrade my radio and speakers. How does the radio come out?
The shaft-mount radio comes out in a two-part manner. You pull the knobs and use a socket or needle-nose pliers to remove the nuts around the shafts. Then you remove the whole radio pod by removing the screws holding the ashtray brackets to the dash and the screws by the steering column, in the glovebox, and hidden at the top. There is a mount in the back of the radio, and sometimes it's got a rubber tip on it that rides in the hole and other times it's retained by a nut.
You then need to get an adapter for the stock harness and run some ground wires out to all four speakers. The old Motorola radios grounded through the body or used a common ground for all speakers but that will fry most newer radios. Trailer connector pins are the correct diameter for the speaker connectors, and the three-prong power connector is a plug type used for ages.
Check this motorcycle site to see the "OEM-Style Non-Latching Connector Shell Pairs" for the power connector. The "trailer connector" pins are .156 (4mm) bullet connectors (standard bullet connectors are 3.5mm) and can be bought in the correct 4-pin square style. (And that's why crimp connectors are always loose in cars.)
All AMC's used the same 5-1/4'' speakers in the front doors. I think the back speakers were all originally 5-1/4'' as well, at least in sedans and 2-doors; sometimes the back speakers were originally 8Ω so be aware if you reuse them, but almost all were 4Ω. I forget what factory speaker connectors were, but I have a feeling they're related to the three-pin power connector.
I've rewired radios in every car I own, and believe me - you don't heavy wire.
18 gauge will get you there. I've become a fan of not removing good working factory connectors unless they're impossible to find, then I go with molex or weatherpack connectors because they're dirt-common and don't come apart but you need a good crimper and not the cheap auto store one.
Good luck!