Thanks for the input. I'll probably just bite the bullet and do the swap to front discs since it seems almost impossible to find the coarse spline birfs. I still haven't quite figured out the scrap yard / surplus dealer network here, so I guess that will be this weekends project. If anyone knows...
I recently purchased a 75 BJ40. It is early 75 with the drum brakes and coarse 6 spline hubs. The previous owner removed the front carrier and inner axles and I am working to get them replaced. The consensus seems to be to swap all of the parts so that you get the disc brakes and the fine spline...