205-70 14 or 215-70 14 Both excellent choices for what you are doing.
The last thing you want to do with the little slant motor is to dog it with a big tire.
Here is a 215 70 14 on a 65 Dart
PS: 70 series for 14" wheels 60 Series for 15" wheels.
That looks great...as usual with your stuff....BUT the 215 70 14 is about an inch shorter than the 235 60 14, so on the rear, the 60 would not cut the gear ratio quite as bad.
