State Parks suitable for 40' Fifth Wheel 13' 6" tall

Ussually I use the rvparkreviews site to find campgrounds along our route of travel and it's worked out OK with regard to commercial parks. I'd like to stay at more state or federal parks but am really concerned about getting into a situation (or park) that is a mess to get out of. As an example, we just left the Blue Ridge Parkway and looked at several of the campgrounds on the parkway - most were listed at rvparkreviews as big rig accessible but I couldn't have even made it into the entrances, let alone into any of the sites or through the interior roads.

For those of you with Big Rig type RV's, is there a relatively easy way to determine ahead of time if your rig will fit into the park and sites?

Even calling the parks directly has given me mixed results: often the person manning the phone at the park knows very little about RV's or has even been into the campground.

I'd appreciate any advice or tips.