Rear shocks don't lift tacomas, there's no perch to adjust. They can accommodate lifts up to certain levels without topping out tho.
Rear lift comes from a pack, an aal, a progressive aal, or..... *Gasp* blocks
That said, runnin too long of shocks and no rear lift out back can give more droop but less up travel. I tried tundra 5100 rears with a 1.5" icon progressive Aal. The droop was AMAZING, the ride was plush as hell on small bumps... But the lack of up travel caused the shocks to bottom out before making contact with the bumpstops, which happend on a pothole (terrible feeling). My up travel was very very small, and I went back to the Tacoma 5100s and it's been fine.
I'd rather have more uptravel instead of more droop on my truck personally. That way throwing 1000lbs in the back leaves me with plenty of travel before coming into contact with the bumpstops, and avoids bottoming the shock itself.