Nice project. Looks like you're making good progress.
The first one of these top breaks I had was given to me by an old friend. It had a broken main spring and hand spring. I made a new main spring easily from a K-frame spring by shortening and thinning it. The hand spring drove me nuts though. I tried umpteen different attempts before I hit on the right springiness, strength, size, etc. This was pre-Google days, and I didn't even have a decent picture to go from. I finally had success though, and now understand how some goat herder can spend his evenings in a cave pounding out a beautiful replica of a 1911 Colt.
I'll tell ya, I was good at tearing that thing down and putting it back together after doing it seventy eleven times. The bore was terrible on that pistol, but it still shot good, and functioned perfectly for years; until it got stolen by a tweeker chick.
I was bummed about it for years until I adopted the one at the top of this thread. These little gems will always hold a place in my heart. jd