'75 318 exhaust help

Treblig, then you are the man to talk to. I guess for me larger would be better! I mean, my 318, with all the pollution crap on it, was only rated at 145HP. Car is not even on the road yet, but starts every time and runs good. The exhaust is going to be my winter project. One of my goals is getting the HP up a little bit ( maybe 200- 225?), but still trying to stay drivable. I eventually want to put a different intake & 4 bbl carb on it, (like H22's thread, '75 Scamp) but after reading all the threads about A-BODY header hassles, I'm not ready for that yet. I'm a rookie and just want bolt on parts for now, until I learn more. Everything on this car is stock. Will large hole 340 manifolds work and just bolt on to my stock heads? It needs a new exhaust system anyways. It's a 904 trans, with 2.45 gears in the rear, so it's just going to be a cruiser. It's even got the fuel pacer light on the fender. Remember the oil crisis and need to increased gas mileage? I was 17 in '75, just missed all the good cars. I'm greedy, I just want it to sound like more! I'll have extra cash in about 6-7 weeks, (Bonus!). Thanks & please PM me with a price, if your manifolds will work for me.