Bodega, you don't have to have a crossover, just like you don't have to have headers. But they remove a lot of the harshness from the exhaust noise and actually improve exhaust scavenging, because some cylinders are ideally timed in their firing order but they are on opposite banks of the engine. With the crossover, the suction they produce after their pulse helps scavenge the next cylinder better, even if it's in the other bank.
H-type and X-type crossovers are the two types. There are rpm ranges where each one works best. X-crossovers are exactly as you describe, and generally build better low end torque and high end horsepower. However, from about 3500 to 5500 rpm, the H-pipe works better, perhaps because the X-type might tend to "over-scavenge" at certain rpm ranges.
Summit sells an excellent X-pipe really cheap, along with mandrel 45 degree bends to make it all work. Just cut and weld what you need.
I suggested the X-pipe because torque is important in a truck, and because 283's don't have as much low end torque as 350's, for example. So I figured this would be the right choice for a truck. However, if an X-pipe doesn't fit right (like in my Corvette sidepipes), then an H-pipe might work better. It all depends on what's right for you.
For example, I have a street/strip 1968 Firebird with a Hipo 455 bored 0.040" over. I have my stall selected at 3500 rpm, which is right at my torque peak. 455's redline at 5600 rpm, unless you have really expensive connecting rods. So I chose the H-pipe because I need max power between 3500 and 5600 rpm.
On my IROC, I have a mildly souped up 355 Corvette motor. It makes roughly 2.5 times as much power as the original 305 did. But because it's got a torque-building tuned port induction set up on it, I used the X-pipe. Tuned ports are all done by 5000 rpm or so, so 80% of the usable power band is covered by the X-pipe's response characteristics. And it really works. That car accelerates out of the hole like a cannonball. I don't worry about high rpm power because the tuned port isn't made for that. So I maximized torque. And that's the criterion I would use to select that crossover for your truck.
This is wordy, I know. But hopefully informative.
