- One-Class Era-
The first ten years of the HOPRA Nationals from 1975 through 1984 only featured one car class each year. There occasionally were a couple drivers class designations, but the cars were the same each year. However, the rules changed, sometimes significantly, from year to year. This ranged from full near-unlimited (1975, 1978 & 1979), to various restrictions on magnets and electrical systems. The in-line G-Plus format was heavily featured in years 1979-1984.