Call up Longfield Axles.
I agree with JRock 100%: call Longfield yourself so you are satisfied with a correct technical answer, but I will mention that I have also researched this path you are describing, and I contacted Longfields just before they had taken delivery of their first sets of 30/30/30 spline chromoly 80 series superaxles (which differ from their earlier version of chromoly 80 series inner axles, which had the same 30/24/30 splining configurations of the stock length inners and birfs). It surprises minitruckers sometimes to learn that 80 series stock axles are 30 spline (same as minis) at the outside of the birf and where the inner shafts plug into the diff, but they are 24 spline at the CV or where the inner axle plugs into the birf bell. Many people, like me, thought that once someone like Longfield or RCV produced a fully 30 spline 80 series chromo set of inner axles and birfs, that they would be interchangeable with other fully 30 spline inner axles shafts of varying stock or even custom lengths; however, when I called to order a set of the new Longfield 80 series fully 30 spline Superaxles, but with custom length shafts for 67.5" 80 series custom front housing, I was told that such 30 spline 80 series shafts had a special taper where they plugged into the CV or birf, and they were not interchageable with "cheaper" custom length minitruck 30/30 spline inner axle shafts. Also, at that point in time 01/2013, I was told that custom length 30/30 spline 80 series inner axle shafts with the special taper on the birf side (which only Longfield has been selling) were only available in stock lengths.
Bottom line from my research is that if you want an 80 series set up front without oddball lengths, you can keep it stock with 30/24/30 spline birfs and inners, or you can upgrade to the same configurations, but in Chromoly sold by Longfield or Nitro, or you can upgrade to a stock length 80 series chromoly set with 30/30/30 spline birfs and inner axles sold only by Longfield.
Here is a link to discussion on the subject previously posted on pirate, which is nothing definitive, but gets into questions about custom length inners:
http://www.pirate4x4.com/forum/toyota-truck-4runner/1170242-fj80-rear-taco-rear-ff-conversion-w-ifs-hubs-63-5-width-4.htmlIf I were you, I would get the axle set up just how you want it in terms of WMS to WMS width, using 30/30/30 chromoly birfs and inner axle shafts made for minitruck/FJ60 axles with custom length inners. If you are worried about odd ball lengths, you might be able to plan for a centered rear axle set up that uses the same length of 30/30 spline inner axles shafts that you would use in your front axle's longside axle shaft. Posting later in that same thread above AKAdventurer proposed the following set up, which looked interesting:
I am guessing that AK may be planning for trail repairs and with this 63" front and 60.25" rear configurations he could carry a spare 31.5" 30/30 spline inner axle, and a 30/30 spline 17.25 chromo inner axle shaft, and a 30/30 chromoly birf, which would cover breakage of for any of his axles front or back or side to side. Maybe a bit overkill in planning, but peace of mind for sure if you add maybe a spare set of knuckles, studs, and other high quality spare parts.
It is also interesting to see that his diagram notes which sides for e-locker engagement based upon the type of diff used. I am not sure if making all of the 31.5" inner axle shafts (including the spare) long splined to work with an e-locker would hurt. I would probable skip e-lockers myself and keep it a bit simpler.
