According to the guys and gals from the USA on the Classic-Celica web ring, 18/20/21 and 22R engine sumps are interchange-able, so you *should* be right.
I would assume that you would swap the oil pick-up at the same
time.
One of the more popular mods for them is to fit a 20R head to a 22R motor and drop that into a 18 or 20R engined RA24/29 Celica.
Cheers,
Mitch.