Julian,
I believe the MSD 8521 is still available by special order. You can also buy the appropriate Accel Dual Sync distributor, throw away the cap and rotor, then cap it off using an Autotrend EFI cap (http://www.autotrendefi.com/distributor_cap.html). If the crank wires and connector bug you, simply remove them.
PANTERA INTERNATIONAL
A DE TOMASO CAR CLUB
Presents the De Tomaso Forums
The On-Line Meeting Place for De Tomaso Owners and Enthusiasts From Around the World
Clicking on the banner will take you to the sponsor's website.