I hooked up an got a set of FJ40 disk brake axles in 3:70 gearing.what you need is the companion flange to match the dimensions of the later diffs which are a larger pattern than your current 1972 flanges.
it is easier to get the slip yoke end which will slide into your existing driveshafts and swap the driveshafts so the slip yoke is towards the diff end. that way you have the correct length driveshaft with the correct flanges on each end.
the u joints are different also between early and late.
need a zip code for a shipping guess.