Welcome to the forum and irv2.
What your looking for maybe hard to come by and its possible there is no room in floor plan to do a lift.
Here is a Brochure
and Owners Guide
The 2013 Canyon Star
has a handicap lift built in the latest coach's the last two years and this year Newmar add two DP's in their line up for the handicap.
In this link
you can see a video and floor plans of the newer handicap coach's Newmar put out this year and some conversions handicap members did to their coach's.
We also have a handicap forum
that you can ask members questions also.
The 3508 you maybe able to put a lift in the door way
for someone to get in coach kitchen is on opposite wall.
Good luck in your pursuit.----2006 Scottsdale