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I want to remove and replace the bolts and bushings on the back of my springs on my M38.. Would like to know the best (easiest) way to do this. Thanks

The best and easiest way is in accordance with the steps in the manuals. I strongly recommend you have three thoroughly reviewed manuals in front of you when you start the job.
1- TM 9-804 or TM 9-8012 M38 Operator's and Manintenance Manual
2- ORD 9 SNL G-740 The M38 Part Manual
3- SM 1002 The civilian CJ2A/3A, 3B service factory manual.
You'll find Chapter S of SM1002 here:
http://www.willysmjeeps.com/v2/modules. ... _album.php

When you say back of your springs are you referring to both front and rear ends of the rear springs or just the rear ends of both the front and rear springs?
You should reference shackle end of spring or pivot end of spring. The pivot bolt is a different size on M38's (7/16") so do not buy a civvy CJ pivot bolt.

I just want to replace the bolts and bushings on the back of each spring.

Again you should do as Wes suggests and read those manuals.
When you say the 'back' of each spring that confuses the question as the back or aft of the front springs is different than the aft end of the rear springs. They are basically the same but flipped 180* so the fixed ends are in the center of the vehicle, on the M38. So with that, the fore end of the front springs are the shackle end as is the aft end of the rear springs.
So what is it you want to change, the shackles or the fixed ends. They are 2 entirely different jobs.

The right hand and left hand thread part is important too!

Even the lug nuts on one side are right hand and the other are left hand for taking off the wheels.

Those manuals may take some time to read through, but will save you hours of frustration and $$$ in broken parts.