Great photos,
I watched a similar major rebuild at Bourn without the aid of a jig!!!!!!!
When we tried to fit the main gearbox the ring of bolts at the bottom was half a hole out.
Then we tried putting the ring of bolts in first. The only way to get the A frames aligned was to put all the shims in the front on one side and all in the back on the other.
A lack of clearance between the fwd tail rotor driveshaft and the centre firewall was ignored and a brand new shaft was written off when it contacted the said firewall.
Then they built a jig!!!