On the inside of the firewall are six blind nuts - four for the motor mounts and two for the long-gone nose gear mount. They were removed by threading in a 4mm bolt...
... and tapping on it until the blind nut came loose. They weren't glued in place so they came quietly.
Next step was to drill out all of the holes (8 x 1/4" and 1 x 3/8"), clamp on a back plate...
... And tap in some dowels.
