Today I drilled a hole in the stock and tried the push pin method. I set up my arbor press with wood blocks to rest everything on and used a bronze pin to push against the shaft with. The spring is quite easy to compress with the arbor press but unfortunately, the shaft is also forward of the hole once I have lined it up side to side. The lever tool looks interesting and it seems there is a relief in the wood for something, maybe a lever. The V-notch screw driver and hardened pin seems that it has an advantage in being able to push the shaft in the direction(s) required. I'll let you all know what I end up doing and thanks again for all the great ideas.

Gazz