OP depends on what you classify as "Old Days"
BITD 1974 era we only had these classes:
Mini
100
125
175~200
250
500
Ltwt ~Hvywt Pro
That's it ! no: a, b, c super, vet, novice, big wheel, 30, 40 senior, etc etc etc.
NO SANDBAGGERS either, plus we ran longer motos and never got our second...