You will hate it..
those fords with 4 spd trans have tall gears. there were aux trannes made to go behind the main trans in order to slow the ground speed down but not slow the pto.. howard made one to go with their rotovator tiller.. and everett made one for a trencher. either of those would work fine.. without it, unless the soil is loose sand.. you will be making umpteen dozen passes to get anything useable.
I've actually seen a guy till with 2 ford tractors one in neutral revved up running the tiller, and the other creeping along at idle pulling the other tractor.
At a MINIMUM I'd use a 5spd in an 800 series.. or more preferably, one of the 8spd machines.. alternately, the 10speed power shifting SOS trans would do it well.. if you could find a good working model.
soundguy