Just to add, if the isolators are installed correctly (top and bottom), then check the coils orientation. The top coil edge or the face at the top end of the coil should be parallel to the axle and placed towards the outside. To be honest, between the Watts Link and the Shocks (and rear anti-sway bar if equipped) limiting the suspension travel, the springs should not have popped out, even if one used 3" slammer springs. Could remove the springs and compare them. You might have got a mismatched pair. There are front & rear coil spring dislocation cones available for 4X4's to keep the springs from popping out. Might want to see if any of them fits as a last resort.
From the service manual (sorry no pics, scanner is down):
INSTALLATION
(1) Install a rubber isolator on each end of the coil
springs wrapping the rubber fingers around the coil
(Fig. 32). Turn the isolators until the rubber abutment
butts up against the flat end of the spring coil.
NOTE: Both ends of the coil spring are identical.
Either end of the spring can be the top or bottom.
(2) Place the coil springs on top of the axle spring
perches.
(3) The coil springs require proper orientation to
the body when installed. To do this, turn the coil
springs (along with the rubber isolators) until the
flat end of each upper spring coil lines up with an
imaginary line running parallel with the axle beam
as shown (Fig. 33). Also, make sure that the upper
coils end near the outboard sides of the vehicle and
not 180 degrees of that location.
(4) Raise the transmission jack guiding the coil
springs into the spring mounting brackets on the
body of the vehicle. Raise the jack until the shock
absorber lower mounting bolts can be installed
though the axle brackets and shock absorber lower
mounting eyes (Fig. 30).
(5) Install the washer and nut on the end of each
shock absorber lower mounting bolt. Tighten the
mounting bolts to a torque of 88 N·m (65 ft. lbs.).
(6) Remove the jack.
(7) If equipped with a rear stabilizer bar, hook the
lower ends of the stabilizer bar cushion retainers into
the slots in the back of the axle, then rotate the
opposite end of the retainers upward so the mounting
bolts can be installed. Install the mounting bolt
though each cushion retainer into the threads in the
rear axle (Fig. 31). Tighten the rear stabilizer bar
cushion retainer bolts to a torque of 61 N·m (45 ft.
lbs.).
CAUTION: When installing the watts links and bell
crank to the axle, make sure the bell crank is rightside-
up. When mounted properly, the words BACK
UP should be able to be read from the rear over
the top of the axle (Fig. 34).