Don't worry too much about going with garbage can diameter fuel line just yet. Work with what you have. Find and SOLVE the issue before throwing money and parts at it. I mean, even as well-intentioned as it is, we here still act like a government- spending other people's money.
If you find out the fuel line is "hosed", then fix what's broke. Nickel/Copper line actually works pretty well as a fuel line. I wouldn't ever use plain copper alone as a fuel line. As with any fuel line, route it away from heat sources and keep it from vibration wear.
While a cat converter pluggage issue is not out of the question, if it revs well and is repsonsive to the throttle while unloaded, then it's likely not your cat clogging. That pancake style converter that's under there is pretty archaic though. Easiest way IMO, to determine if your cat is clogging is to run the engine with a vacuum gage attached to the intake somewhere. Start slowly increasing engine RPMs and if vacuum goes away or runs toward zero or engine dies, then you MIGHT have to investigate a cat clog. If you still have good vacuum, and the engine isn't choking, it's unlikely there's a clog.
