My edelbrock carb is running rich. I was told I have to rebuild carb because it is a chance that something is blocking air and not mixing with fuel right. I had the car setting up for a while then I drove it a little bit and it sat up for a while. Im sure the gas tank is like crap in the inside. How hard would it be to replace the tank? Is it hard to do?

It's not hard at all. It's a little time consuming and you need a helper. I replaced mine with a brand new tank and new sending unit about a year or so ago. The old while your at it thing...replace all your hoses and clamps and stuff, their pretty cheap. Make sure you disconnect all your fuel lines at each end and blow them out with air to clean them out. I sprayed something in mine and blew them out but I don't remember what it was. Someone here will probably tell you what to put through there. 

Its pretty easy I have replace the ones on my 70 and 81. It might be cheaper to buy a new tank then have it dip and clean and lined. Once its down it would be a good time to clean up the rear in and the tire carrier.