I have several Blackhawks I have worked over. Get a spring kit from Wolfe, or Power Custom, or Brownells, or etc. The kit will have trigger return and mainsprings in it. Tear down the pistol and install the kit. While you have it apart, seize the moment to clean, deburr, and polish anything that needs it ( hammer strut, hammer, etc.) No need to polish on the sear surfaces.
Get a belt mountain base pin while you are at it, and install.
Reassemble and try it out. You will be pleasantly surprised. The Ruger BH is pretty easy to work on.
Tom