[Speedy Jim]

This works if you are alone:

Shift in gear (any gear).
Handbrake on (or tie wheels down so they can't spin).
You can apply a very light coating of lube to the splines.

Push engine in and at same time very slowly turn the pulley.
It should plop right in.

This assumes that the clutch disc has been centered when you
installed the disc and that the shaft splines aren't buggered.

 

[Speedy Jim]

he'd left a nut on one of the bottom studs

HaHa (Wasn't so funny at the time...)
BTDT

Worth checking