Locked in Gear or Neutral - Shifter

[Orange Truck]

I have a 1969 Chevrolet C10 Stepside with the gear shift on the column. On occassion it will lock and shifting cannot be accomplished. There are two arms almost below the master cylinder fluid container and nearer to the firewall. To unlock it merely requires raising the hood and either lifting or pushing down on the the shifting arms. Somewhere I seem to remember a discussion on this subject and it is related to wear of a part or parts on the column. Can anyone comment and offer a suggestion as to how or what can be done to prevent this?