David,
Very nice restoration on your Delta 6 X 48. I have two to restore, I plan on donating one to my local high school wood shop. I'm new here, I kind of got here backwards.
I belong to another forum, I nope I won't get into trouble posting it, they could have really helped you out during your restoration. If you join, they have a section called BOYD (bring out your dead) where you can post wanted ads and for sale ads as well as get great info on machines.
They can help you out on info on crowning your sander drums. Heck, I can help you, the easiest way to do it is to cut a 2" strip on your 6 X 48 belt then you can rip it all the way around so you have a 2" wide belt, then install the 2" belt to drive the upper drum and use the rest to crown the drum as it goes around. When you're done with one side move the belt to the other and do that side. Use a good straight edge to check your progress. It's not that important that you get it perfect, just close. The website is OWWM.org for the forum. For info, pics and machine manuals, got to OWWM.com
Hope this helps you and other folks.
David
OOPS, I didn't see where Pikeman had the same idea.... David, do you need the threaded rod that applies tension and the spring?