The ramp is called an rti ramp if you want to search the internet. You drive up the ramp till a tire comes off the ground.
If you take the measurements I described frt and rear it should get you close enuff for the proper shocks you need. You'll need some jackstsnds under the frame to get the...
Driving up on those little blocks isn't going to give you any info. Measure the shock mounts pin to pin on level ground, then measure the distance between the bump stop and axle and maybe add 3/4 of an inch +-, and subtract that from the pin to pin measurement. That should get you close to the...