oops my bad lol. i was thinking of tht application on one side of a v8. its 6 into 1 guys, i apoligize
If you want your 6 cyl. to sound better, buy a set of kook equal length headers with merge collectors. It will have a sweet tone and a nice rumble rather than what you get with your cheap, rusted out, junk yard headers.
Actually, the 300 swap is a good. You will have to fab the mounts or make a motor plate. Dad built one waaaay back in 1970 to run in NHRA H/Modified Production class. He used the 300 block, 300 crank, 240 rods (they're longer), custom piston, solid lifter cam (couldn't afford a roller), ported head with Pontiac 421 intake valves and Boss 302 exhaust valves. Crane triple springs and 1.73 roller rockers, Clifford research intake with three Weber 48 IDA downdrafts and a Vertex magneto. Borg Warner Super T10 hooked into a shortened Dana 60 rear with 29x9 slicks. All of this tucked nicely into a 1965 Falcon Sprint. Buzzed that thing to 7800 rpm and held the national record for part of the 1971 season at 11.17/116 mph. Swapped the record back & forth with Glenn Self all of the '72 season until he parked the car. Just couldn't afford it anymore with two kids. One of the best things you can do is put a Fluidamper (or equivalent) on the engine so it doesn't shake itself apart.
The only sixes I've heard with headers had the split ones (3 into 1) with dual exhaust. Nothing you can do there to kill the crappy sound, except run them both into one large exhaust pipe.