We'll he's not in the OC but Jason at Rancho Motorsports can take care of you on all your needs. He actually quoted the same spindle lift for Shipping guy once for me and the prices were very good. I think the cast spindle is plenty strong for your truck...if it was the heavier diesel I'd probably recomend the fabricated spindle.
As far as lift I believe the spindles will give you four inches of lift over a stock ride height. It would be a good idea IMO to use those and crank down the torsion bars for a better ride and less wear and tear on the front end.
Call Jason and see what he can do for you....might be worth the drive (909) 390-9722
I also don't think you'll have any problem fitting that tire. I ran 285/75R16's on my stock height 2500HD with the 6.0L gasser with a little trimming and maybe one crank of the T-bars.
Try looking at a 305/70ish tires for a fatter tire. The 295's are a little narrow looking in my opinion. Jason can tell you what works well with that lift.
Good luck,
Chris