Do you really think a 1975 PA28 flies differently from a 2000 model?! They have the same instruments with the exception of a different layout and a GPS which you should not need at that stage anyway. All aircraft are checked every 50/100/150 hours and annually for commercial operation with the engines inspected at TBO regardless of airframe age.
Oh and I did my commercial licence at a school that had a fleet of 1980s Senecas.