Scope to Dot adapting??

Im working on my old High Standard 103 supermatic. It has worn a old Tompson Center pistol scope since the 60's and Im looking to move to a dot sight. I was thinking it would be easy being it already had a mount, and it would be a easy swap... NOT!!!   Turns out the mount, and scope is backwards from the norm. The rail is in the scope, and the...  Ill use the term "gripping part" is on the base. Is there some adapter to adapt a dot to this style of mount??  Anyone been down this road before?

Here is what I have now....  not a real clear picture...

Looks like the original TC scope mount.  Dig up a weaver base and drill it to match the holes in your barrel.

It is also the mount that Bushnell used. I found a replacement at Optics Planet. This is a pic of the original Bushnell and a mount with 30mm rings.

I think that Al Marvel makes a base for your High Standard.