coilover spring rate

I am considering converting to 18" triple rate coilovers in the front end of my 73. It does have a Windsor and a winch and plenty of tubing. Any idea what main spring and tender spring rates would work best? The helper spring is 5" and has a rate of 20lbs/inch.
Thanks,
David

Most of the ones I have been arround are about 225/250. I did talk to a guy running 250/300. However I'm sure there are others who can tell you more than I can.