I have rusty's 6.5 long arm. pushed to 8 with shackles and adjustable coil spacers. Did not need to change the control arm length when I added the spacers up front. my lowers were 36"or 38" sorry can't recall but the uppers were 16" (For sure on that number).
When I put the 38's on I actually lengthed the front arms by about 5/8th of an inch to move the front axle forward.
Stock shackles are around 1.5 inches total eye to eye I think.
As to adjustments on the arms, put the axle where the tires clear the fender wells(Lowers) and the caster is within tolerance (Uppers). First might want to leave the lowers alone, lower it, and adjust the uppers for caster angle. And see how the tires fit the fender wells up front (When turned). Pretty simple really. there are other things though, like steering gear binding at full flex, but I assume your going for a lower daily driver, so probably not a real issue.
HTH