Your box (parallelogram) is a great visual in this case. Each corner of the box must pivot for the suspension to travel. Anchor one corner and it will lock the box and there will be no movement.
In your diagram points (A) 5549, (C) (D) 5500 are obvious pivot points, not so obvious is (B) 5555. See my attached red-line. In order for 5555 to pivot, bushing 5537 has to allow vertical travel. If the spacer 5540 is too long or this point is bolted tight, this corner is anchored and the suspension binds or locks the box.
This was Anders orginal observation, too tight and there's only 2" of travel, the looser he makes it, the move travel he gains. Make sense?
Hopefully Anders can find the infromation he needs from Rare Parts.
EDIT: these bushings 5537 are actually acting like coil springs, in that case the spacer lenght should not be as big a worry, if the bushings were reproduced, maybe the hardness of the bushing is too great, like have too high a spring rate that they can't be compressed. Looking at the photos Carl supplied, that looks more like the bushing height I'm use to seeing, I was surpised to see the lower bushing listed as being 2" tall, in Carl's photos, it's been compressed quite a bit.
1959 J Convertible
1960 J Hardtop
Last edited by GTE427 : 03-07-2011 at 03:04 PM.