I'm on your side friend; I like 'em on second gen Barracudas.
If you have less than about 40degrees of overlap on your cam, then long-tube headers are more or less optional.If you have more than about 60* overlap, then you gotta have longtubes to wake up the power. So that means IMO between 40 and 60 degrees you have to make a judgement call, based on how the car is going to be used.
But.... A right angle off the end of a long-tube will kill the scavenging anyway so then it all goes out the window. You might as well put a teener cam in at that point..... well that might be a lil extreme.
So if your 340 is running the stock 114 LSa cam with 44* duration, just run whatever you got.
Here's an idea I once had for my 367. She runs a 61* overlap cam and so I run TTI's. I have run as much a 76* with a different cam. The overlap period of that cam was an unreal power booster.
So the idea I had was to run a big plenum off the end of the collector straight back to where the mufflers usually sit, and turn them 180*s there with 3" mandrel tubes, then come into the side pipes from the rear, and dump at the front. Bad idea that was, cuz now the exhaust wants to come into the cab.
So then I had another idea, to run about a ft or ft and a half of collector extension and put some cutouts on he ends there,then Tee or Y into that extension anywhere and run just enough diameter pipe off the extension to run up to 3000/3500 rpm into the sidepipes. Then the cutouts I wanted to run were out of Australiia, and were automatic and instant-open/instant-closed; Yeah baby,I though; this will work. But a short time later when I checked back, that link no longer worked, and I never saw them again.
That is still my idea to do someday......... but I guess I'd have to build my own dumps.
But I gottawarn you, the sidepipes I handled were HEAVY, and IIRC were
small ID.. You'd probably need a 360 just to pull the extra load, and plow exhaust thru 'em,lol
