How to check front spring bushings

I would say your FLD has traditional grease type pins and bushings. I check them on the ground with a long bar between the spring and hanger. A block or spacer can be used to get the leverage in the right spot especially on trucks with tall shackles. The new joint will have zero movement. A slightly worn one may have 1/16" or slight more before greasing but may have some life left. Getting toward 1/8" is time to re-bush or new springs and hangers some prefer. Severely worn bushings that have lacked lube may have bushings squeezed out the shackle side edges and or may be even worn into the spring. Once the pin hits the spring it will not hold a new bushing very long due to the egg shape.

I use a 5/6 foot regular angle tip prybar or my favorite is this-----

https://www.amazon.com/dp/B002SZVJR...olid=23A8I4HZBAWD5&psc=1&ref_=lv_ov_lig_dp_it

Non- serviceable rubber bushings can be checked in the same manner. Usually there's more of a gap between the springs and hanger on these so you can start to see the gap/separation between the pin and rubber. Any contact between the spring and hanger or spring and shackle on these is also an indicator the joint is seporated or worn out.