What length to use for campgrounds max? With or without TV?

We love national forest campgrounds and use them often as we travel. We have found that if it says 38-40' and sometimes even 36', we can fit our 40' motorhome and Jeep in the space so I would say it's the RV length. However, we rarely make reservations. We'd rather see the sites. We do pull in early in the day and during the week - not weekends.