Wow. 600 miles in 8 hours? Unless my math is wrong, that is 75mph - - without even factoring in fuel stops/rest stops. Too fast for me.
To your question, RV Life Trip Wizard can do what you want. You set your basic input - things like speed you want to travel, fuel tank size, mpg expected, etc and then you can opt for driving hours per day or low/mid/high mileage per day. The map then shows distances (rings on the map). It will show just about any kind of campground you want - - - private, KOA, BLM, State, County, and on and on. Not free but a good program.
https://tripwizard.rvlife.com/
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2007 Sierra 2500HD Duramax | ECSB
2012 Rockwood Minilite 2104 - Purchased 08/2012 - Sold 07/2022
2022 SOB 29' 5th wheel - purchased 09/2022; 400w solar on roof; 150w suitcase kit; 206ah LiFePO4; 2k inverter; boondock ready