Stumped with rear shock length..??????

The old 2" longer than stock in the MP chassis book has served pretty well for 40 plus years.

Same as the 70-71 Imperial shocks,I run those... (002,3 springs..)The Cal Tracs ,might like a different idea.. Again ,it's tuning /log keeping & experience, to learn. R.R.R., all we can offer is advice, from experience. O.P. needs to wrench,& learn.