Thanks for all the replies.
Three point hitch setup is definitely NOT OEM. The tractor was originally owned by the Country DOT, had a side mower (sickle bar), mowing hillsides. Second owner just used it for pulling a large old reel mower. I'm the third owner. Good news is that the engine doesn't burn a drop of oil (never had a plow on it).
Bad news is that bottom hitch bars are NOT Ford. Measure 32" long center hole to center hole. With the bottom hitch bars horizon, they are about 5" past the rear tires. 6' blade should be able to swing around, maybe the 7' also if it is offset.
Lots of good info here. thanks for any more comments.