I don't know that either are a true crossover. I assume the D235 is a 23.5 PTO HP tractor which puts it right with the 1720 ( 23.5 PTO HP/ 28 engine HP). The 1720 also uses a 3 cylinder like the D235, where the 1920 uses a 33 HP 4 cylinder engine. It looks like the trans and shuttle are similar to both model Fords. My guess is the D235 is closest to the 1720 in specs but as far as being a direct parts crossover, I can't say. It may have exact parts or it may simply share some parts but have unique parts specific to each tractor.