Macs Mids to LT's
IMO, go with the long tubes and have done with it.
However at lower and mid RPM's, the mid-tubes do not make nearly the amount of power that LT's do. The LT's have much better savaging down low and the gains are not just a handful, they are tremendous.
Here is a graph of before and after. I was running AS&M mid-tubes and switched to LT's:

Look at the differences under the curve.
When I put the LT's on, it had so much more low and mid power you would swear there were 2 more cylinders in the motor.
So the answer is yes. There are huge gains when switching from mid-tubes to LT's when you factor in the big picture. The proof is in the graph.
IMHO, the only reason to have mid-tubes is if you need to be emissions complient. Or if you are lowered.
Trending Topics
The Best V8 Stories One Small Block at Time
For full disclosure, there was a spring change (now that I remember) in addition to the header change being represented in the graph. I installed Patriot extremes and that 100% cured the float problem and extended the very upper power to 6.5K or so. I would not expect the spring change to show any difference on the graph from 6K down.
But you can see, the header difference represented is striking.
At the time, I had a 350 with LE2 heads and an LE1HL cam.
I did the swap after driving in a friend's TA with similar mods + LTs.
http://cranecams.com/?show=newsLetters&no=239
his car also was swapped over from mid lenght to long tubes years ago with back to back dynos and picked up 2 hp and 2-3 trq.









maybe true duel 3"?