S2A Drives well for 10-15 min then struggles when warm

Hello everyone!
I just recently purchased a 1962 Land Rover Series 2A. When i make quick .5 miles rides to the store and back its fine BUT if i drive further distances (maybe a mile or 2) and it requires going into 3rd or 4th gear and starts to warm up thats where i start to have issues. After its warm, if Im going from a stand still the truck will loose power and barely get home. Today it got even worse. Drove for 5 min, pulled up to the garage, put it in 1st, engine cut off. Started it again, tried to go into first and died again. Reverse kind of worked, but eventually i put it into 4Low and got it to go forward.
Heres what ive done so far:
-Replaced fluids in transfercase
-Oil Change
-New Dynamo (charging light wouldn't turn off, now its turning off and the battery is charging)
-coolant topped off
I am in texas, so its hot. It has overheated in the past to the point whre coolant is coming out of the radiator cap so i think that may be the culprit, waiting on a new thermostat and will do a full coolant flush this weekend.

Anything else that could be causign this loss of power/inability to move in first after warming up?

What engine is it? Will it rev in neutral? Any misfire?

Assuming it's petrol.

Could be evaporation of the fuel in the fuel lines.

Could be the fuel pick up pipe in the tank part blocked.

Or could be the coil breaking down.

Check all and replace the fuel system.
Check all and replace the coolant system.
Does it still have a fan and cowl on the engine?
Check all and replace the ignition system.
Chances are no one has looked after it properly for years, you don't really want to keep over heating it.

Wildefalcon said:

Assuming it's petrol.

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Then my first check would be to replace the condenser and check the points

After you have driven it and it has played up have a feel of the ignition coil. If hot likely as @Wildefalcon says above it is breaking down. Also as @kermit_rr post replace the points and condenser.
Do you have a Temperature gauge fitted?

tottot said:

After you have driven it and it has played up have a feel of the ignition coil. If hot likely as @Wildefalcon says above it is breaking down. Also as @kermit_rr post replace the points and condenser.
Do you have a Temperature gauge fitted?

Click to expand...

The coil will be warm, but not too hot to touch