I'm wanting to change the intake and exhaust and carb.
what are good intakes and exhaust for the 300?

 

It all depends on what you want to do with the truck in the end.
There is nothing wrong with the factory setup in my book.

On my 81 I kept the factory intake & carb hoping for good MPG but running EFI exh manifolds 94 Y pipe and factory replacement system to tail pipe.
I am not running a cat but do run a Thrush welded muffler.
I use the truck for weekly home trash runs to the dump, cruise to cars & coffee and club shows and when nice out to / from work, 40 miles each way.
I also built it as a back up to pull my open deck 20' car trailer.

Others seam to like the Offy intake manifold and a v4 carb and a header.
I seen where the v4 carbs are hard to tune, might be to big cfm for the motor?
Headers leak, not so much at the head like a v8, on the only straight six I had a header on it did not leak.
That truck had a v2 intake from the factory and ran a Holley 2300 350 cfm v2 carb and ran great.

And others also change the cam for something a little bigger and / or run Chevy rockers.

You have to remember the factory had to build it to be reliable under all conditions.
When you start to "hot rod" a motor some of the reliable part goes south.

How will it run when cold out? Will you still have the hot air going to the air filter?
Most likely not as it will be open and that is not good for power as it is pulling in hot engine bay heat.
Same goes for heating the floor of the intake manifold when cold.
Aftermarket carbs will need adjusting when the weather changes to run tip top, factory dose not change as much with weather.

Dont get me wrong I do like a nicely done mod straight six but also a factory looking one too.
Mine looks factory even with the EFI manifolds.
So it comes down to what are you looking for in the end.
Dave ----