Having ordered springs before, (Powells) you also need the number of coils per the 3.3" length, as well as the diameter of the wire itself. The latter makes a huge difference on the compression numbers of the spring. For example, this is how "Century Spring" lists theirs. I was particular on what suspension I was looking for. (Or you can dig around hardware store bins and hope for the best)
Coil Springs Manufacturer - Stock & Custom - MRO & OEM | Century Spring Corp.
O.D: 1.562
CENTURY STOCK NUMBER: 895
FREE LENGTH: 4
ID: 0.996
RATE: 497
SUGG. MAX. DEFL: 0.74
SUGG. MAX. LOAD: 367
SOLID LENGTH: 3.08
WIRE DIA: 0.283
TOTAL COILS: 11
MAT’L: HD
ENDS: CG
FINISH: Z
Cost: $16.82