"Split-Case" Transfer Cases came factory in 8/80' - 1/90' FJ40, FJ60 and FJ62 Landcruisers. They derived the "split" name as they require being "split" to remove or install them on the vehicle unlike the earlier 1 piece cases. These cases came in at least 5 different configurations, most changes being minor with the exception of the idler shaft change. In April of 86', The idler shaft changed from its original 34mm OD, to a slightly larger 38mm OD. This makes external identification of the transfer cases rather easy. Simply use a set of calipers to measure the idler shaft wher it protrudes from the rear of the case. With the change in idler shaft dimensions, bearings, seals and internal gears were also slightly changed.

34mm Idler - Manual Trans. Setup (H41/H42/H55F)
(8/80' - 4/86')
Input shaft: 19 spline
Input Gear: 34 tooth
Primary Idler: 45 tooth
Secondary Idler: 25 tooth
Hi-Speed Output Gear: 34 tooth
Low-Speed Output Gear: 43 tooth
PTO Gear: 31 tooth
Total Low Range Reduction: (45/34) * (43/25) = 1.3235 * 1.7200 = 2.2764

38mm Idler - Manual Trans. Setup (H41/H42/H55F) & Auto (A440F)
(4/86' - 1/90')
Input shaft: 19 spline
Input Gear: 32 tooth
Primary Idler: 43 tooth
Secondary Idler: 24 tooth
Hi-Speed Output Gear: 32 tooth 
Low-Speed Output Gear: 41 tooth
PTO Gear: 31 tooth
Total Low Range Reduction: (43/32) * (41/24) = 1.34375 * 1.7083 = 2.2956

38mm Idler - Manual Trans. Setup (originally mated to H55F)
Input shaft: 19 spline
Input Gear: 32 tooth
Primary Idler: ?
Secondary Idler: ?
Hi-Speed Output Gear: ?
Low-Speed Output Gear: 38 tooth
PTO Gear: ?
Total Low Range Reduction: 1.999?

8/80' - 10/82' - 34mm idler shaft, unique input gear. No oiler cup provisions. No spacer bolt hole.

10/82' - ~83' - Same as earlier case, with updated input gear, possible introduction of oiler cup provision at this time. Unknown if middle mount bolt hole exists.

~83' - 4/86' - 34mm idler shaft. Has oiler provisions. Has spacer bolt hole.

4/86' - 8/87' - 38mm idler shaft. Has oiler provisions. Has spacer bolt hole. Different gear train, bearings and seals from 34mm cases. 

8/87' - 1/90' - 38mm idler shaft. Auto tranny version. Vacuum 4wd. Has oiler provisions. Different gear train, bearings and seals than earlier 38mm cases. 

4/86' - 90' - 38mm idler, no oiler (might have been an auto one I had without oiler provisions?)

Vacuum Shift - Manual Shift Conversion (courtesy of rick_d @ ih8mud.com)
90254-05004 roll pin for front axle op rod
36313-60050 rod front axle
(then you need a hollow 15mm nut, spring, and ball, drill and tap)
(common to 34/38mm manual cases)

36307-60030 lever arm hi/low
36362-60040 gold cad arm for lever above
(common to 34/38 manual cases)

machining is there for front rod seal.