I don't know about the Rebel, but I change my M1 Cree to the SSC Flood Kit I got from battery junction, that worked out well.
I also have the M1 Lux3, so I decided to put the Cree in that one, found out that the lux3 model has a shorter head so the longer reflector will not fit, had to use the old one. I did manage to put in the Cree, but had to screw the light module in just a few thread and not all the way in till it bottom out. Turns out the lux3 module is shorter then the Cree and the SSC P4 Module.
This might not answer your question, just be aware that the M1 comes with different length head. Hope this help.