I presume you will go to lillooet via highway 1 to lyton. That part will be no problem. From Lilliput be ready for gravel rd and steep hills with tight switchbacks.
If you want to go via whistler to Lilliput the Duffy is paved, steep but easy. I take a 36ft thru there regularly.
If you decide to go via Pemberton and the hurley be prepared to shake your teeth out on that road.
1999 Winnebago Chieftain
1992 Jeep YJ
1984 Harley Liberty edition