OK, I'm still debating my path on my car. I basically am looking at two options. Either doing the motor or exhaust first. I can't afford both at the same time but will complete both in progression. I am either gonna put a 350 in and use factory exhaust or freshen my 305 up and go for headers, y-pipe and cat back. Which would be the better area to attack first? How much power would a full exhaust make over factory on the 305 and how much would it rob on a 350 making in the 300 range? I know that's a loose question but just looking for a ballpark.

 

If you indeed have an L69, its exhaust is not as restrictive as an LG4 or LO3. It is still a bit restrictive, so headers and full 3" free-flowing exhaust would improve either the 305 or the 350.

Doing headers at the same time as the engine swap would be less work. But, if funds are truly your limitation, then it really doesn't matter.

Again, though, exhaust would improve either engine. But, the 350 should have more power than the 305, even with the stock exhaust.

I would NOT bother freshening up the 305. That would be a waste of money, if the eventual plan will absolutely include a 350, and would mean it would be even longer before you could do the 350.

 

Having experienced a junkyard junk 350 with LG4 exhaust, I thought it was fine, up until about 25 MPH. Then it ran out of breath. Then it shifted out of first gear, and I wondered if the 2.8L V6 might be any better?

 

Honestly I would save my $ a lil longer and do the 350 swap w/exhaust at the same time. It would be easier and the exhaust is a must when really trying to add any power to these cars.

 

V6 and LG4 / LO3 used 2.25" single, L69 was 2.75", so somewhat better. I've seen aftermarket cats for L69 be made from 2.5" expanded up, and from 3" pinched down.