Need guidance on getting 340 running again

Good Morning. W/O getting into too much personal detail, I have come into possession of a 1971 Demon that hasn't been running in 5/6 years. I was present at purchase and it ran and drove. It had some wonky wiring under the hood and I couldn't convince the new owner to purchase a new wiring harness before running it. Within a month it smoldered and melted some the wiring under the hood and in the column. He took apart the dash/column and ignition to assess the damage and that's how it remains. Under the hood is untouched from when he bought it thankfully, but there are complications when I get there. It has the red box ignition system, aftermarket Accell coil, high rise intake manifold, and a split (double) fuel line to carb (unknown make at this time), amongst other things. I need to get this car started within 2/3 months. I have a new Year One engine compartment wiring harness, but before I get to the wiring issues....The fuel has been in the tank several years and needs to go. I would think that has to be first. After I syphon what I can in the tank, I'm assuming I have to drop the tank to get the remaining fuel out. Or will it evaporate if I leave the cap off? That seems unlikely to me. What do I do about the filler stem? Is there any issues I don't foresee in taking it out? What do I do about the gas lines up to the carb? Do they need to be drained? I doubt there's anything in there after 5 years, but is there something I should do? Cleaning somehow? I guess I could just try an external gas tank to start it but it's got to be done eventually. Once dropped, is there anything I should do to the tank, or ways to determine if I should just replace it? I prefer to stay original if possible but if I can see issues, that's different. Once drained and put back in must I put fuel in immediately, or can I leave it empty/drained until I figure out the wiring?

Next would be are there any mechanical issues I should be concerned with in trying to start an engine after 4/5 years? Is there some maintenance to do? Things to check or test? Sorry I don't have any pics yet. Thanks