The short tube headers are based on the Fentons, so it really doesn't matter which ones you use, performance wise. The tube ones are cheaper, but will rust out eventually, unless you get the stainless steel ones. Iron is better in the long run. Both have provisions for running heat tubes up to the intake, or you can run water to the bottom of the intake as well. There are plate kits out there for doing that. The early Fentons with the heat riser built in are very had to come buy and are very expensive if the seller knows what he has.
There was a test done in Hot Rod magazine that clearly demonstrated the differences between open headers, crossover pipe, no crossover, and X pipe. No crossover was the clear looser. As I see it, the more horsepower you make, the more benifit you get from it. Since a 235 makes a whole whopping 140 gross hp, a crossover might get you another 2 hp, but I think the main benifit for our inlines is in tuning the sound it makes more so than worring about the HP it makes.
A freind of mine has a '52 Belair with a stock cammed 235 with Fentons, Smittys, full tailpipes, crossover, and bazooka tips, and it has the best idle sound I've heard yet. About as close to a V8 as you'll get with 6 cylinders. It isn't as "quiet" as some would have you believe, once you wind her up a bit she'll bark nearly as loud as the true duals and glasspacks on my '53. I intend to add a crossover this year with a flanged connection in the middle so I can experiment with it to see how changing the amount of block off affects the sound.
If you run a muffler that has the two sides mixing together, then adding a crossover wouldn't make any difference, as the muffler is doing it for you allready. I noticed an "X" stlye 2 in 2 out muffler in my Jegs catalog the other day FWIW...
The farther forward the mufflers are, the louder it will bark ( with full tailpipes)
In the end its entirely up to you how you want to run your exhaust. There isn't enough performance difference one way or the other on a 216/235/261 to warrant a ****ing match....
