These flanges are approximately 3 inches in diameter and are held together using 4 bolts. Also, each driveshaft flange has a centering ring on it that is approximately 1 inch in diameter and protrudes approximately 1/8 inch beyond the face of the flange. This ring serves to accurately align the two flanges to a common axis.

Over the years, Toyota used at least three different flange designs for these purposes. The flanges differ in overall flange diameter, bolt hole size, and bolt hole circle dimension. In general, it appears that the early year models used smaller size bolts, and the forward output flange on the transfer cases has a larger overall diameter and bolt hole circle than the other flanges. However, as far as I have seen, all the flanges seem to use the same centering ring dimensions so that any driveshaft flange can be axially mated to any third member flange.

For the purposes of building custom driveshafts, or mixing different year components, it is possible to modify the flanges to mate non-matching pieces. Flanges with the same bolt circle, but different size bolts can simply be drilled to accept the larger bolt size. For flanges that also have different bolt circles, simply offset the flanges 45 degrees from normal (see above diagram) and redrill one flange to match the other. Clamping the flanges together while drilling will help ensure an accurate match.

Having your transfer case flanges drilled to accomodate more than one flange pattern may also serve some benefit when it comes to building or swapping spare drivesafts.