Be aware that you can not use the stock 15" wheels with the CPP 6 lug conversion as the inside web of the wheel will not clear the calipers...
Can you suggest appropriate sizing for wheels?
I have installed the CPP 6-lug disc kit on my '51 and of course you are correct (not that I doubted). I have ~ 1/2" spacer on there right now, just so I can move it around.
What specs do I need re offset/back-space?
I'm probably looking at replacing with an OEM looking wheel but with modern radials. Perhaps a smoothie ...
Nothing outlandishly wide nor large diameter/low profile
Advice appreciated!
(even 6 lug wheels from other models I could consider?)