George,

If the car still has front and rear subframes and the original floor
and firewall, the current rules will basicaly apply except for the
tube-frame stuff. Other than improvements in safety equipment
and changes in weight, engine prep and suspension rules have
not really changed. I guess you will need a '70s copy of the GCR
and Sedan category specs.

The MG Metro Turbo brake calipers use two lines going to each
caliper, one to each side. You will have to connect them together
to a T junction. I used to have a set on my Mini. They take an
LD65 pad which you can get from Hawk or Performance Friction.
The non-vented rotor version of that caliper was popular on
S2000 cars.

You probably won't find a good set of used drop gears available,
but you can order them direct from Jack Knight.

Joe