Hi all, I’m a Rhino beginner who wants to make some optimizations to an open source 3D model, but am unsure of the commands necessary to do so.
Some changes are a little easier than others; I have listed them all in the attached Google Doc: Adjustments to Parts 3 and 4 - Google Docs
In the Google Doc, each required change will be preceded by a sort of index (i.e 1A, 1B, etc.)
When providing assistance regarding a specific change, kindly refer to this index for ease.
Please let me know whether any changes seem unclear, thanks in advance for your help! 
I have attached the 3D files in question below:
64 Craftsmen Short Gear.STEP (951.2 KB)
64 Craftsmen Long Gear.STEP (625.2 KB)