JAR 737-300 rating covered non EFIS & EFIS on the groundcshool, allowed to fly both types, and some with clockwork engine instruments but EFIS EADI & EHSI.
The rating covers from 737-300 to 900 series but NG differences training(usually a day or two) is required before being allowed to use the rating on the newer types. Also diff training before 40etc. 200 series is not included and is a seperate rating.
This was the JAR(UK) situation last yearwhen i did it, believe it is still the same.