Replacing coil Springs: Help
 

Hi all,
New here. Just bought a 2000 Grand Marquis. It needs shocks, springs and likely other suspension/steering parts. I purchased KYB gas-a-just shocks for front and rear. I am considering variable rate springs for the back as I do load the trunk up with drums, wood, etc from time to time. The roads are not great here in Rhode Island. I was looking at the MOOG CC865 for the back. Should I get variable rate for the fronts as well? Recommendations? On a budget and I am pretty sure I will need to replace other parts. Going to do the rear shocks and springs first and fully diagnose when I get it on the lift. Doing the work myself at a DIY garage. $25/hr to rent lift, tools and the owner will help in a pinch. Thanks in advance
PS I have been getting squeaking/grinding noises which I just read could be due to the spring insulators being bad. I kind of figured that I would need bushings as I think the car may have sat a long time.