good choice, those were good looking trucks!! it depends on the state of repair (or dis-repair) the truck is in. as far as the engine, if youre actually going to use it for its intended purpose(hauling stuff) you would be happier with a v-8. if you are dead set on a v-6, there are a few of larger v-6 ford engines (4.2, 4.0 pushrod, and 4.0SOHC) that make some good power. there was also a 300CI (5.0L) pushrod inline 6 that made loads of torque but got horrible mileage. something to consider if you use one of the listed v-6's is that they were all fuel injected and you would have to adapt a wiring harness to an older truck which can get very difficult really fast. look into your cheaper carbureted v-8 engines such as the 302w, or 351w. good luck, and take your time with repairing and you will learn a lot!!
