Coach #3764

[AMD103]

Just recently I came across a Spectrum Coach #3764 Item No. 89003.
I know it's very old and it could have been a kit.
I'm experiencing a problem attempting to replace the couplers[horn hook] with knuckle couplers.
Can anyone shed any light on how to go about this or is there a knowledge base to reference how to solve my problem.
Thank You in advance for any and all information that you can share...

[ACY]

If your coach is Spectrum then it most likely originally had a knuckle coupler. Of course if it is in the range of 25 years old then it may have originally had horn hook couplers. The coach was not a kit as far as I know, they never made them as kits.
If all else fails, remove the existing coupler box/assembly and replace it with a body mounted coupler box (ie Kadee). Bear in mind that doing this will require you to have about 24" minimum radius.