Move Tickets from one instance to another

I’m in an interesting situation and have been scouring the wiki and threads
to find an answer, all to no avail.

My organization has a main RT instance (3.6.4, everything working smoothly)
and a secondary instance (3.4.5) which was set up for a small subset of our
users. The employee who configured the smaller instance has left the
company, and in the interest of streamlining things, we’d like to combine it
into our larger instance. All of the queues, cfs, scrips, templates were
easy enough to move over (there really weren’t that many) but the group
using the instance would also like their 600+ tickets moved to the new
instance. To make things more interesting, most of these tickets have at
least one file attachment.

I put together a scrip and template in the small instance that will email
all of the ticket information (comments, correspondence and field
attributes), but I can’t manage to get it to attach the files and send those
out as well. The idea behind this approach is that I can have one instance
mail the other, thereby avoiding any issue with conflicting IDs-- once the
email reaches the primary instance I’ll have a scrip decode and apply the

Has anyone attempted to merge a smaller instance into a larger one? Does
anyone have a scrip/template that will send whole files out as attachments?

Thanks in advance for any help/input!