HO Acela to add NWSL Stanton drive

[Swingkingokc]

Our layout has 3 & 4 % grades such that the engine
cannot easily pull the grade.  I plan to install
the "Stanton" NWSL motorized trucks under cars to
add power to smoothly pull the grades...
?What is the spacing (in scale feet) between the
Axles?  What is the size of the wheels on the
Acela passenger cars (29-32-35-40?). 
What Digitrax chip is recommended to
run with the Bachmann chip in the
existing engines of the set?
I noticed that the N-Scale sets use a similar

Scheme for their power.