Here are these Milestar 13" tires on my Dart:
Last year I posted this about the same problem with 13" tires:
The challenge is not what is an equivalent tire size from a conversion chart but rather what tires are still made and sold right now! That is the challenge.
There were two sizes...
A vacuum gauge is very useful for showing what might be going on. Hook up a gauge to the manifold vacuum port of carb and take video of what it is like at idle, then goose the engine and quickly let go of the throttle to check the internals of the engine. You can look at the many vacuum gauge...
Just a side fact about the 1964 Dart radiator: Since the V8 was a late addition to the '64 Dart they did not use a different radiator support panel than the /6. Therefore the radiator is noticeably off center with the fan blade on '64 273 V8's. The fan blade overhangs to one side.
But I doubt...