The actual engine won't matter, as long as it's 60's to 80's 350. What matters is what pulley set up was used. Does it have a short or long water pump? 67-72 trucks used a short water pump set up. 73+ used a long water pump set up. This changed the pulleys/brackets and their positions. Either set up is easily swappable, but for everything to work properly you need to use the correct water pump, brackets, and pulleys that were meant to work together.
You'll probably need to post pictures for help on this.
You can see some of the differences in my thread here (I had a long water pump set up and wanted to switch back to the correct short water pump set up):
http://www.67-72chevytrucks.com/vboa...d.php?t=249479