Alot of new cams are split duration ,with higher lift and duration on the exaust,which leads to a different spring than the intake or shimming it for more pressure.
Ideally they should be the same and on a mild 100,000 mile engine they are ......but in a performance engine ,you should never take the lbs rating to heart.Usually each individual spring gets set with a shim for installed pressure and over the nose pressure ,resulting in each spring being a different installed height.The engine does not care ,as long as you have the proper lift clearance on the springs to prevent coil bind ,the rest gets made up setting the valves and push rod length.
On a real race motor ,probably every single spring is a few thousandths different than the others to get the proper seat pressure with in a few lbs along with the over the nose pressure,alot of the time its a compromise on the seat and the over the nose to get a good installed height ,without stepping up to a taller spring or a increased rate per inch,but thats probably out of the scope of this build ,I thought I would just throw that out there for infos sake.