Are your tires loaded or do you have wheel weights?
I had a John Deere 850 4wd gear that pulled my 72 inch blade but with difficulty. I now have kioti 2610 HST. Both machines have loaded tires but the kioti is heavier, so that has no problem with the 72 inch. I also run an 84 inch rake with no difficulty.
So long as you have the weight, you should be able to run the 84 inch and that way not have a wheels wider than the blade when angled.