Cheapest high flow cat for my chevy?

[Skunksmash]

I'm looking for the cheapest high flow cat that you guys know of. Mine seems to be clogged up or is getting clogged up. I'm pretty sure I have the original cat converter on my truck from the 80's lol. Its huge and its pretty old looking.

Its single exhaust too... not sure what the diameter is. Was it 3"? Just the standard Y pipe that would have came on the truck. 87 model with 350 engine. I want to cheap out on this one. Don't have a whole lot of money since I just bought a boat, and its just the catalytic converter, so eh, not a real fun part to spend money on. I'd like one that's direct fit with the pipe diameter and is high flow.