I have the rcbros.com conversion, similar motor mount to rcmikes. if it is in the stock position, you have around 90mm from the plate to end of the chassis so it will fit that way. my motormount is 38mm tall, which puts the middle of it, at 19mm. so if all my math is right, the radius of your motor is 22mm. which means you will have to raise your motormount up 3 mm, or carve room in your chassis(not a good idea) for it to fit.
If you dont want to do that, if the 1512 in your slash is
not finned, it might just fit without any modifications.
here is a pic of my mount, to put things into perspective, and see if it applies to you
