I think the adaptor was machined from a big sized plate, and it uses unique bolts that have about 1/4" thick head and screw in with an allen wrench.
The plate re-locates the starter position, so a notch has to be cut in the transmission bellhousing for the starter.

The adaptor kit was pricy, I think around $500!

Here are some related links:

http://www.hotrod.com/howto/43323_mopar_overdrive_transmission_swap/index.html

http://jvxracing.com/jvxcatalog.pdf

Let me know how the megasquirt works out, I might try that in the future...