Okay so right now i've got a 305 in my T/A pushing 358hp at 5,800 rpm and 342tq at 4,000 rpm. I am now planning to redo the exhaust from the headers back, so I am wondering what is the best:

Headers to use? (long or short)
Pipe size? (I'm thinking 2.5")
Muffler or should I just go straight?

pretty stout 305 you have. my opinion

-Dyno don shorty headers and Y
-no less then 3in pipes
-Performance muffler, best flowing is magnaflow, if you want loud then flowmaster

What have you done to the 305?

Currently I have replaced the cylinder heads with a pair of Iron Eagle S/S heads that have a 165cc intake, 76cc combustion chamber and 1.94/1.50 valves.

Replaced the Cam with a flat-tappet hydraulic Cam from Comp Cams.

Replaced the intake manifold with a Edelbrock Performer RPM AirGap.

Had the carb tuned by a GM mechanic.

There are a few more tiny odds and ends but thats the big stuff.

long tubes will serve you best. 2 1/2 inch collectors. either merge them into one 3 inch back or run duals with an x-pipe to balance the exhaust pulses. then put on a good muffler either dual or single out.