The 75 hatchbacks have some differences compared to the later models. Some were good and some were bad, but there are a number of subtle differences that make the 75 a bit more unique. The dash is one of those things, personally I like the 75 dashes better but I am a bit biased
The floorpans have a higher tunnel because the Monza was originally designed to have a Wankel rotary engine which has a higher output shaft compared to traditional engines. The 75's had the carry over Vega solid front disc brakes and small rear drum brakes as well as the new 262 V8 engine. Later cars had some improvements like the vented front rotors and larger rear drums, also a 305 V8 was introduced. The 75's was the only year for the curved panhard bar on the rearend, later cars had the straight bar.
Fortunately most of the improvements that came on the later models could be swapped on to the 75's. Of course the 75's were the only year to come from the factory with 350 V8's if you were in California. They were in a pretty anemic state of tune producing something like 145hp but it did give you a excellent platform to build upon.