Pretty simple swap really,other than maybe having to torch off the bed bolts from underneath,sometimes they spin where they are square in the hole in the bed and you cant hold them from spinning...the wiring harness will plug right in,keep the one off the stepside & the tail lights if possible..
There are some 8 foot stepsides ,so dont get one of those if you want a 6 foot one!..I think they are the same from 73-87 and possibly even farther back that 73--I think 67 -87 are the same...you may have to drill a few bed bolt holes as some years had a different number of bolts holding the bed on...