A W tire is pretty wide. With a bunch of inner fender modifications, I was able to squeeze a 29.5 x 10.5 under the fenders on a 15x10 rim with 5.5" backspace. I doubt a W would have fit without a fit more modifications with a BFH.
A 29.5 x 10.5 has 10.2" of tread and a 13.1 section width.
The 29.5 x 10.5W has 11.2" of tread which to me shouldn't qualify as a 10.5 tire and has a section width of 13.6" wide which only puts it 1/2 inch wider than a non W tire.
I ran those tires for 2 years then back halved the car and now run 32 x 14 tires.
You need to do something like this until you get enough clearance.
