Just did two trips to Yosemite in April and July as my son was working at the Ahwanhee Hotel.
We have a 40-foot Tour and tow a Jeep. Of the hundreds of campsites in the Valley, only TWELVE fit a 40 foot rig and ZERO will fit a 45 footer. We had site 111 in North Pines both times.
If you don't have a campsite, parking for a 40 or 45 foot rig is very limited and in the summer impossible to find. The main loop road is fine to drive on but the campground roads are tight will all the trees.
There is a big parking lot by Curry Village and some parking along the road between Curry Village and the campgrounds. Space will depend on the time of year you are there.
Read the posts about the best way into and out of the park. Rt. 41 from Fresno is the easiest.
Tom and Katharine
'07 Winnebago Tour 40TD, 400hp Cummins
RVing for 19 years & 150,000+ miles