Give BritishStarters.com a call. Modern gear-reduction starter motor, drop in replacement. I have one in my car, Dave the Wave is now using these in his cars as well. More reliable, more powerful, lower current draw.
I have also gotten mine from BPNORTHWEST. Great guys ! I ran one on Blugill for 4 years, no problems. I also have used the starter to load it onto the trailer when the fuel pump quit. Pulled it right up! (second gear)