The only way to do this correctly is as specified in the factory manual.
Tighten the shackle bolts until they are snug but do not torque them. Same with the nuts on the end of the bolts.
Drive around a little to settle the springs, then do your final torquing. This locks the inner steel sleeve of the bushing to the shackles at the correct position which should be about halfway through its available travel.
By doing it this way, getting the bushing torqued down with the vehicle at resting height, the rubber in the bushing has the ability to absorb the spring movements without stretching too far in one direction and possibly tearing.
FWIW, front shackles should be at about 60 or 75 degrees off the chassis. Rear shackles should be closer to 45.
The methodology of torquing the bushing at its resting position applies for any similar metalastic bushing. On the coil sprung vehicles, if you torque your panhard rod and trailing arm-to-axle bushings while the vehicle is a on a lift and the axles hanging down at full droop, don't expect a ton of life out of the bushings.
1960 SII 109" Tdi- "Red Square"
1984 90 Tdi- "Yamelo"
1988 RRC- "Chewbacca" (lives again)
2008 RRS SC- "The Supersofa" -wallet thinner
1972 SIII 88"- "GreenHELL" now in NC
1959 SII 88"- "The Little Green Beastie" last seen in NY
1988 90 "Eric the Half a Bee" half a truck, sold for parts
1991 RRC- never got a name- long since recycle
1987 RRC- "Chewy 2" Sold 12/18; now in NJ