17" will be a tube-type multi-piece wheel, and 17.5" will be tubeless one-piece.
They may be three-piece wheels (I know that at least a lot of the 60-66 era 17" wheels were). If they are, there will be a big snap ring in between the outer rim/ring and the center/rest of the wheel. EDIT: And the outer ring/rim will be a solid/continuous ring as you described.
Last edited by 66Submarine; 05/30/2014 6:21 PM.
Some of my crap:
1963 C-30 flatbed dually 292/SM420
1965 C-10 LWB fleet 250/column shift 3 speed
1965 C-30 9' stepside 250/SM420/4.10 gears (my DD)
Website I made for my crap:
http://www.66submarine.com 
