FYI a moderator moved your original thread to the Monster Truck section and there's more replies there. Here's the link:
http://www.rctech.net/forum/monster-...ess-motor.html
The inside diameter of the Losi mount is 43mm. You could shave down the little nubs/heatsink of the motor but why? The HPI motor is made by Castle to HPI's cheaper specs, so the Castle is a better motor that fits without mods. You really should check out your original thread, I posted some important information about the limiations of the Losi mount you need to read before buying a motor.