Shift lever will not lock in park

[StefanW]

Hi all. I have a 72 GMC. I just put a tilt column in it. I believe it's out of a 72 van? I have all gears, back up lights and the wheels lock (you can't turn them) when trans is in park. It will only start in park or neutral. You can however pull down on the shift lever, without pulling it inward, and the tranny will shift into reverse, neutral, drive, etc. You cannot shift it into park without pulling the shift lever inward. You can shift into any gear using the bracket (where the linkage attaches) on the outside of the trans.
I have tried many things but I can't get the shift lever to stay in park without pulling the lever inward first. Is it something inside the column? Could it be a spring or something inside the tranny? If it was the parking pawl the wheels would spin in park correct?
If anyone knows what the issue is or has any suggestions on how to fix this, please let me know. Thank you in advance.