Is there any difference between the Atlas 73 and 74 models?

[martinjdoman]

I am planning on refurbishing my 74, using pieces from a 73 that I just picked up yesterday off FB Marketplace.
Does anyone know if there is any fundamental difference between the two models? The only thing I have noticed is that the 73 is green and my 74 is grey.
I have looked at the diagrams and they seem to be identical on first purview...