Laudanum, be aware that JBL periodically makes a batch of kits for a legacy driver, and when that batch is gone it can be a few years before another batch is made. I suppose the demand is too low to keep every kit in stock all the time. When I had my LE-8's reconed, I sat on them for many mobths until a new batch had just appeared after several years of being unavailable. As far as I know, JBL never admits there will be another batch, or gives a date for it - you just have to keep checking.
Also, a friend who was less patient bought an aftermarket foam surround that was specifically designed for the LE8-T. It was so stiff that the resonance frequency doubled, to around 80Hz! So just because the part is an exact mechanical fit, it does not mean that it is a suitable part. In the case of the LE8, I suspect that the original surround is not available because it is subject to foam rot, and new ones - even the JBL - are made from a more resiliant material and are at least a little stiffer.
I have not put mine in a box yet, but I am looking at Clark's "Thrasher" box for experimenting; I think it's around 3 cubic feet. I had another pair of LE8's re-coned as 2115s, 3dB more efficient but not quite as flat a response. I am looking forward to comparing them!