From memory, I made two short pins to hold the two 'tubes' together and held the balls in place with grease.
This assembly was put on the end of the spring guide and pushed into the main cylinder using a spring compressor until the ends of the short pins were visible through the holes in the main cylinder.
Then the proper retaining pins were pushed into the holes which pushed out the short pins out the opposite side,

Hope this helps,

Best regards
Bill.