I made a quick and dirty scope mount for my 513T by grinding down the bottom of the rear of a Marlin lever rifle scope. mount to fit over the receiver, about 1/8 " for a length of about 1 1/4". Finished it off with a file and stone, and rounded out the center of the mount with a 1/2 round file over the last 1/2" at the receiver. This was a Weaver mount, takes 1" weaver rings, and is available from Walmart for cheap. I use a 4x Tasco deer scope with it, and it is extremely accurate,though a little heavy.
I just had this mount in my parts box, and the holes fit the rear holes in the Remington.
For what it's worth.