Back spark plugs?

I have the car listed above supercharged. It sat in someone's yard for close to 10 years. It had a crank no start problem. The gas was turpentine. I hand wiped the gas tank. Replaced fuel sending unit and pump, fuel filter, oil filter, changed oil, new oil pressure switch, changed crankshaft seal and crankshaft position sensor and camshaft sensor. At that point it wasn't getting an ignition pulse. I replaced the PCM, and it started right up. I changed the thermostat and radiator fluid because it was overheating. I've barely driven the car. It runs really rough, has a misfire and still gets hot after a period of time. It almost seems like the cat might be clogged also. So, when I drive it it has no power, is sluggish, and runs rough. Can I get to the back spark plugs okay? And what is a good way to clear the cat? And would those issues cause it to get hot, misfire and possible cat clogged? I haven't pulled the water pump and it doesn't appear to leak but that may be a possibility for the heat as well. Any techniques to reach those back plugs and do you think I'm looking in the right place for the next steps. I don't mind buying coil packs plugs and wires as a set. I found all of them I can get for about 75 dollars on Amazon. So I was thinking about just updating all of that. And then for the cat? What do you suggest on that? Thank you