Will 1" coil spacers up front help give better traction out back? Cause my truck has that front end sag plus all my body bushings are in great shape so I know its not them before someone asks. Also has anyone used a rear sway bar kit on the 81-93 d series and how much difference does it help?

I put a swaybar on my truck and it did make a big difference,but I put a front one on at the same time.

In theory,yes. Shifting the weight rearward helps traction. In reality the weight bias will improve less than 1%.

We need to know more about your truck. At this point I'd say tires would be a giant gain vs the minute gain from a front spring spacer.