74171 Special shoulder bolt that mounts overdrive adaptor to original David Brown gearbox casing, 2 extra required as we use 3 original correct bolts  - modified over original, replaces 2 of the shorter bolts that hold the speedo drive housing on the back of the std gearbox.

The one stud listed is the same as one of the std gearbox rear speedo housing studs so is not required new.