If you haven’t already, download a 65 Plymouth service manual from
MyMopar - Mopar Forums & Information - Service Manuals
Here is a simple step by step process for TDC. And should only take a couple of minutes.
I don’t mean to offend or doubt your abilities by restating this. I want to be absolutely certain before you go to the next steps.
Establish for sure that you are At true TDC on compression stroke.
1. Find compression stroke on spark plug hole #1 by placing finger over plug hole, crank engine with starter until you feel the air pushing by your finger, stop cranking.
2. Place a stiff wire or coat hanger in #1 spark plug hole, hand turn harmonic balancer nut (crank shaft) clockwise (from front) if the piston is already going down, go back to step 1, as you have already passed TDC, if piston is still on the rise keep turning the engine by hand until the wire stops coming up. That should be true TDC on the compression stroke. You cannot gage this by looking at your valves. You need to be directly on the piston.
3. Take distributor cap off and verify that the rotor is pointing towards wire #1. If it is 1/2 way around, lift distributor out and turn it 1/2 rotation and re install.
You should be able to do this whole process in about 10 minutes.
4. If at TDC your harmonic balancer didn’t lineup with the timing marks we can address that later.