Mike,
The differences, if any, will be very slight. The Glenfield line was/is the name that Marlin chose for their national accounts such as the major hardware chains, large department stores,etc. Any differences will be cosmetic and will not effect the operation of the rifle. One difference that comes to mind; the Glenfield line used walnut stained hardwood for stocks and the Marlin used real walnut, IIRC
hth