Eric, although I have not seen that specific 1989, or at least with that paint job, it would be a 40' since it has the tag axle. All of the 40' 1989's I am aware of used a Detroit Diesel 8V92 with an Allison HT 740 automatic transmission. Recognizing that Newells are custom built, the drive train COULD be different based on customer request but the 8V92 was Newell's "standard" engine for 1989.
As to issues with state parks, it depends on the state. Some state's parks are more accommodating to larger coaches than others. By example, California is notorious for having state parks with really short RV length limits, many in the 28-30' range. Yet eight of theirs will accommodate a 40' https://www.parks.ca.gov/RVlength I would use Google to search on "RV Length restriction ____ State Parks" filling in the states you are most interested in.