Welcome!
FYI...you might want to take a look at the factory high performance 1.9 ( non-turbo) that came stock in an 84-86 Impulse for an option to get more power under your hood.
With a little tricking out, they are capable of producing some pretty impressive hp, and you won't have to mod anything because they bolt right in to replace a stock 1.8, since they are both made from the same block.
Plus they weigh a lot less than any V6...and with your present intake, a pacesetter header, an electronic distributor/ignition module from an '82 Luv/Imark/Pup, a cheap high output Accel coil, a weber carb, and a Delta reground cam...they put out somewhere around 125-160 hp, depending on the type of cam and the size of the weber carb.
You can pick up a good used 1.9 from a junkyard for around $200.00-$500.00, depending on where you live, how lucky you are, and what kind of shape they are in.
http://car-part.com/ is a good place to look for stuff if you can't find anything here on the site or on ebay.
Have fun with your truck!