I used 1 full set of tubs cut out of another bed. sliced the stock tubs down the middle.
this will let you tub it right to the edge of the frame brace on the floor botom.
over lap the tub edge and weld it up both sides and along the floor.
little bodo work and hand rubbing they turn out nice and have the stock look. just fat
the aftermarket tubs can be used also. depends on what you up to doing.
as far as rims.. with it tubed to the frame/stock width truck axle you can use a 10x15 rim with 7.5 bs with the 29x15x15 M/Ts (see ricksterhemi black truck for referance)
IIRC, Grumpy posted he runs a 10x15 with 4.5 bs.
my 12x15/a-body axle runs 4.5 bs 29x15x15 M/Ts with stock truck 43" perch centers.