I have a John Deere 8 foot wheel disc. My '44 JD A can hardly pull it in plowed ground on the first pass, and it really needs to be done in 2nd gear; but after the first pass it does it okay, and I can shift up to 3rd. That's a 29 horse tractor, no fluid, with one set of wheel weights. I just started using a '47 JD D this spring, which is 42 to 45 horse power or so, and it handles it really well. Don't know how this compares to what you have, but maybe it'll help.
One of the things I really like about my disc is how well it finishes. It has 14" discs (not cones) and on the outside of the rear gang, the last two discs are 12" then the 10" furrow fillers that extend beyond. This makes a very even transition and hardly makes any disc ridge. You might consider that if you decide to rebuild your disc and intend it for finishing. Keep two of the worn out discs to use on the outside of the rear.