As long as the size of the holes and the distances between the holes is the same then yes 16 inch rims should fit on your truck, the only difference between 16 and 16.5 inch rims is that the flanges are 0.5 inches taller.
Just let your tire dealer know what you want to do they should be able to work something out for you, I went through the same thing with my 77 F-250 camper special it came with 16.5 inch split (tubed) rims which looked horrid which were replaced with some white 8-spoked 16.0 inch rims which looked much cooler.