Lantley, check out sites #1 and either #38 or #39 (whichever is the highest # on the outer side of the loop). The locals with bigger rigs already had those reserved during our visit and I soon found out why.
For #1 (first one on the right) you pull up into the exit of the loop and back straight in. It will handle your 40' with ease.
For the last outer loop spot you start to go up the hill past #1 but then back around the corner and up the exit of the loop straight into the perfectly angled site. Also plenty long.
Have fun, the place and the area are beautiful.