Hi Zach,
I have just recently developed these motor mounts for the Matrix 2 trucks. They might be out of your price range but I thought I’d mention it anyway.
The motor plates are made from aerospace grade 7075-T6 aluminium, which is around double the strength of whats already considered a high grade 6061-T6 aluminium. The stuff is like steel.
I focused a lot on weight reduction for this design to improve board handling, and because of this the mounts require a cross bar (threaded rod for example). They fix to the truck hangar using 4 high tensile grub screws which push against stainless steel insert plates that spread the force and prevent damage to the soft aluminium hangar which can cause mounts to loosen over time. There are some other features such as a slight bump to protect the motors from scratches, small slots to aid in motor cooling, a reversed nut and bolt arrangement, which allows the motor plate angle to be adjusted without removing the wheel, and if you snap a bolt from over tightening it can be easily removed unlike some other mounts which require the bolt to be drilled out (been there, not fun).
I can offer these with all required high tensile steel bolts for $160 AUD for a set of 2 motor mounts, plus shipping from australia. Lead time is currently 2 weeks as they are made to order. I also offer a similar design for caliber 2 and fatboy trucks 