I see. what would be the best way to go about that? how do I take measurements? etc
Glad you have the motor securely mounted and I'm certain the suggestions posted were quite helpful. These guys are quite knowledgeable.
Offset pedal levers seem to all be made about the same, so measurement probably isn't required, though I like your thinking here. The engine drive side pedal lever is the one that needs clearance with some 2 stroke kit motor mounting, but the pedals come in pairs so for both symmetry and having both pedals the same length which makes pedaling less awkward one should mount both offset pedal levers as a set.
The pedal levers are press fit on a square taper shaft and are quite difficult to remove without the simple pedal lever puller tool designed for the purpose, the tool isn't expensive however. Rather than try to describe all this in a post I suggest You tube video how to remove square taper pedal levers and see how these are removed and how to correctly re-install. It will save you a lot of trouble I promise. It's easy stuff once you see it properly done. Getting crazy with a hammer isn't a good idea.
Taking the pedals off remember the right leg pedal has a right hand thread & the left leg side is left hand threaded.
On some newly assembled bikes which are poorly assembled, I've had some pedal levers slip off without using a puller, but if they were properly installed and torqued down; you will need a crank puller tool.
Have fun you're getting there.
Rick C.