If you've got the original engine in the truck it's probably a 230. The same block with a slightly longer stroke makes it a 250. The main problem with getting any performance gains is the cylinder head- - - -there's a big obstruction right in the middle of all three intake ports for a head bolt to pass through. There's a fairly involved modification the hotrodders do that involves cutting the casting, installing short Allen bolts in place of those head bolts, and using a shaped piece of aluminum called a "lump port" to enhance the gas flow. It only makes a difference at higher RPM than most street engines ever see, but it's fun to brag about during bench racing sessions.
If you've got a deep pocket (or own a gas station) the best "go fast" modification other than installing a crate V8 engine is swapping to a 292 inline six. "There's no replacement for displacement!" 292's have got lots of torque, and they'll pass just about anything on the road except a gas pump!
Jerry
