First, welcome to the board.
Second, sounds like a cool truck!
Now...on to the question at hand...
If it were a Cheyenne super bb swb truck I'd restore it to factory spec.....or a highlander or CST with some nice options....
If you're planning to add a/c and highway gears and since it's not in original paint...I'd build the truck the way you want it. If you are concerned with value and making it look like an original, pick a truck you'd like to duplicate. Maybe add a V8 and make it look factory, put in a factory auto column (tilt is a great addition) and go with the style paint you like for 69-70 (solid color or a two tone)
A truck restored with a v8 and some nice options would be worth more than a truck restored with an inline 6 and three speed put back...
You can still make it look like a restored original...even down to having a correct SPID sheet made for the glovebox to match the options you add.