http://www.carcraft.com/techarticles/1311_convert_a_ford_or_chrysler_ignition_to_gm_hei/

with pictures.

I think price is a bit of a wash. pertronix vs the hei conversion.
I prefer petronix.
it literally was the easiest mod I ever made to a distributer.
took 10 min. all the other swaps or replacments always made me reindex the thing so it would fire up the first time.
that was a drop in a fired right up.

never ran one for more than 5 years, but it was still running when I got rid of the motor.