Ryan's M3 medium

[Ryan]

Some more detailed shots showing serial numbers and such.
Centre suspension unit has the cut off remains of what looks like a dozer attachment.
And another shows two different roadwheels. Can someone shed some light on the background of these wheels?
At the moment I am unsure if my tank is infact a M3 Grant or a M3 Lee as it has no upper hull. I have only been told it was a Grant. Is there any way to tell from the lower hull?
ryan