The only grubee i know about with the wide mounts is the GO-Sickem that we can't get in the usa.
The PK80-J does have the wide front mount.
I couldn't say how it will mout to a cruiser.
But it will mount to my ATB mountainbike perfectly.
Look at the PK80-J mount.
I have a little comparison there.
Also my extra supportive custom mounts to beef up the frame.
Gonna need it.
Also notice how i had to drill the frame for the grubbe mount.
Even my 2 yr old can see.
Anyway i have tore apart a Grubee and A PK and writted up all the details if you search for them.
You can make your own descisions on whats better.
I base my findings on whats inside the motor.
I am loving this PK.
BTW when i pull the Grubee off to put the PK on i'll take a good comparison picture.