I didn't see the answers to 2 questions I personally would have asked you
These are not pass or fail questions :p
Q1 : do you plan to add steel bumpers to front or rear in the near conceivable future
If no, 927's w/ 948's or JBA25s
if yes, 790s w/ 948's or JBA25s
Info:
My JBA25's have held up superbly with my rear bumper and ridiculous amount of cargo weight - they're excellent coils
My 927's have NOT, held up to my front bumper
Had i had it to do over, i would have gone with 790s in the front and JBA25, 948s or BDS rear coils, OR.. 4" JBA's with out extra iso's but that's with adding 210lbs-ish of steel to the rear
with no expectation of rear steel I would have
stuck with the JBA25's as well as they've held up with the rear steel I have
running 245-75's you'll have no stuffing issues with 2.5-3" of lift and pushing closer to 4 just accelerates issues with the CV's
no steel, 927's w/ 2-3 conduits in the clevis or a 3/8ths top plate with JBA25/948/BDS rear coils and one or two extra top isos will be adequate lift for 245's, cheaper, and room to grow
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Q&A
What is the difference between a 2.5 and a 4 inch JBA strut??about 1600 bucks

the 4" uses 4" rear coils and a different front
includes front UCA's
the tri link extension to help relieve stress on the rear UCA/pinion angle 0_o
brake line extensions
and i think the front coils are a little longer
Can I use 4 inch struts, and only crank them "half way"??
Is this something I should be talking with Marlon about??i suppose it's possible, but your rear coils are non-adjustable on the 4" and youll be raked ~2"
I honestly think he'd advise you if you want 2.5 to go with the 2.5
Will 4" rear springs yeild the same ride height, or will I be to high in the back??the 4" rear coils will be about 0.75" higher than 948/jba25's with 3 iso's - unless you have something to weigh it down, IMO will ride high and put more strain than necessary, to run 245-75s, on the rear UCA
if you want to run 245-75's the solutions pretty simple and painless, you'll have a lot less headache maintenance wise with the 2.5 range of products regardless
not sure why you'd be worried about stacking iso's in the rear, the upper lip on the rear coil seats is more than adequate to stack 3 total top iso's, they aren't going ANYWHERE