This is an NOS 901 ZF Factory Limited Slip Differential which was used by the Porsche factory in the 914-6 GT race cars. P/N: 901 332 05313.

The ZF LSD requires different drive flange stub axles which are about 3mm longer https://pbase.com/9146gt/image/144205573 than the factory stock units. For more detailed photos of see here https://pbase.com/9146gt/factory_original_9146_gt_parts_901_gearbox_output_flange_lsd