Yes I did. It was easy. I fouind a pair of power trucks on ebay. They dropped right in to the B unit. I used matching decoders. You will also need to add some weight to the B unit. I am very happy with this as my A unit used to slip on some of the grades in my back yard. There is a set of power trucks on Ebay. Current price is about $15. I would grab them and go for it.
It is not quite as easy as stated by Michael if you want the speeds to match for track power and speed sensing. I have done 5 of these and here is what I had to do:
The non-sound block is by far the easier one to motorize as follows for aa analog track powered layout (non MTS/DCC):
swap out the non-sound truck for a powered one.
Find a 4 pin power connector and add at least 6 pairs of back to back diodes on one motor lead to equalize the power to match the A unit.
Tie the power leads to the 2 wire power cable coming from the A unit as well as the inner power block leads.
Add weight over the powered truck.
For the sound block, you need to reuse the sound sensing axle and add a gear to it, and move the sound sensing board to the new motor block, or move the guts from the new block to the old block.
Why not purchase an LGB Genesis unit which uses the same powered trucks. A dealer was selling the Phase IV's for arount $245. But the B unit trucks on the Genny then sell it. Even if you get only half what you paid for it as the Motor Block set sold for $125 or so WHEN they were available.