First of all, great deal Mike!!
I don't do a lot of those but have had quite a few over the years . . . that said I think they are really well "thought out" revolvers. I can't put coil-torsion springs in them (because of their design) but tuning the flats makes a nice revolver!!
I'm pretty sure the main spring is a "drop in" (doesn't have a screw for mounting) so the washer type "strain relief" won't work (good idea though Marshal Will) !! You can thin the width of the main (the time honored way) using a grinder or flat surface with course paper. I use a different method by thinning the thickness of the spring and leaving the sides of the spring alone. This method has worked well for years, I'll explain over in the "shop series".
Mike