Factory amp pins?

Suppose to save some time, tldr is: My rear speakers don't work, the dude at the audio store told me over the phone to check my amp, which came standard but was missing. How can I figure out the pinout of an amp that doesn't fit into the head I have. The vehicle to amp connectors fit already.

I do have some experience with wiring but I really don't want to just bash into this as I've never felt comfortable with amplifiers and the extent of my knowledge is pretty much power and switches. The 95 4Runner I just got had a whole backup camera/Bluetooth/DVD setup in the dash that didn't work, two owners ago put it in and the last owner just dealt with no music. The factory amp is gone so I got one from a 99 tacoma, the next generation. I'd just like to double check that I'm not going to blow a fuse or short anything if someone's got the knowledge.

The amp to speaker connectors fit but the head to amp connection isn't the same, I have a pioneer head that's been in my last two vehicles. If I clip it off and follow the pinout for the head, can I find the correct matching pinout for the amp by creating it from the wire colors on each speaker around the truck? All the speaker wires in the truck match all colors on the head to amp plug but I can't find a diagram for the amp online. The amps model is 86280-35070

The rear speakers also have what I assume to be individual amps behind them, standard. Colored wires go into the board, red/black goes to the upper/lower rear speakers from the board. One amp two speakers per side of the vehicle.

 

I was reading a thread about this the other day on another forum. A guy was saying those factory amps are only 15-30 watts rms and not really even worth running. It may be worth looking into and bypassing the amp and run your speakers straight to your deck.

 

Both sets of rear speakers connect to open faced circuit boards which connect to the deck, it's a separate plug with 4 connections... That's where my limited experience with this cuts off since there's five wires each coming from the wiring harness. Three are the same both side but two are different. I do think if I clipped the matching wires that go into each circuit board behind each speaker and attached them to the speaker directly that would be the bypass you're talking about right? No extra fuses or anything? I'm not looking for a thumping system I just want more than the two tweeters under the dash... Bout to run my own wiring if it's any more complicated than that ^. I would also test from the deck side to the speaker side to make sure the wires I'm using are the same wire, I do know how to do that much at least haha.

 

Im assuming factory speakers? I can't find a for sure wattage on that amp but everything thing I've seen ( second hand info) is 15-18 watts per channel. Which is in my opinion not even worth running. Without looking at a wiring diagram I don't exactly follow how everything is wired. If it were my truck and I was doing all this work I would opt for an upgrade. Atleast after market speakers wired to the deck or get an aftermarket amp and amp some aftermarket speakers.