I have two of the 380 oz motors with 3/8" shafts from Ahren and it does look like the 3/8" shafts are about 1/4" shorter. These motors are installed using DumpsterCNC couplers and I can't easily measure the shafts to prove it. This is just an eyeball comparison.
My early NEMA 23 r&p drives from Ahren have an aluminum pulley with hub for 1/4" shaft.
You will definitely need a pulley with hub.
CarveOne