i had the summit spring fir years, too much tension for me
i just took off the larger one and use the smaller one.
still stiff but much better.
or just go to any hardware store and try various springs
1970 Mach 1 San Jose built Dec 23 1969. Marti 1 of 7. Purchased in 1987. Original family owner of the power train
351C 2v FMX.
1993 GT 13,000 miles, Built 2-12-93 Bought 8/3/93 Auto, 3:27 Axle, cloth, sunroof, AC. Unmolested all original car. Purchased new 8-3-93. still has the factory windshield fluid.