I've had excellent service (six plus years) off road with a BBS02-equipped bike. The motor is a couple of pounds lighter than the BBSHD and arguably "legal" since it's rated at 750w. I've geared mine down with a 30 tooth front chainring which decreases the top speed (on flat terrain) to about 20 mph. I purchased from Luna and have good service from them, but they're not the only vendor. The Trek should make a good donor since, AIR, it has a 68mm bottom bracket which is more ideal for the'02 than 73 mm. Your challenge will be mounting the battery. For 10 miles or so I have a 52V, 4 ah battery which fits in a seat bag. You'll end up adding about 13 pounds to the bike with a small battery (15 for kit and battery minus about two that you remove - crank, BB and front derailleur/shifter.