Frame Rail Side Mount Holes

[fourthirty]

I have a '30 rolling chassis that will become a 255-A when my (honey do list) is shorter. There are 3 dimples in the rail just behind the rear motor mount(on both sides).
Are these the position marks for the side mounts? The chassis is from a tudor with a rear mount!

Thanks,
Fourthirty

 

[columbiA]

Yes,that is where the holes are drilled for S M,s