"Shocks" are two parts really, the damper, and the spring. I would buy the damper and not worry about the spring until I got the the correct fittings and stroke length. I just weighed my bike (CX500) and it came out at 423# total, and 213# front and 210# rear that 50.8% front and 49.2# rear. Now that I know just what the spring has to carry I can buy the proper Spring rate. To find out what your OEM GL spring is call a professional suspension company, someone like Race Tech or FOX, or Lindeman Engineering. They know all the rates and sell the right stuff. With my CX 500 of course I have twin shocks but it's still the same procedure, the damping should match the springing at least the best you can get for your budget.
Cheers, 50gary
Cheers, 50gary