Using a shorting input jack, continuity to ground with nothing plugged into the input jack is correct. This keeps the amp quiet while it’s on with no input connected. If you still have continuity to ground with a cord plugged into the jack, this is incorrect and has been a somewhat common wiring issue with the 2Stroke as the instructions are vague.
Using shielded cable, the inner lead should go from the 68k resistor connected to the tip lug of the input jack to pin 2 of V1, the outer shielding should be connected to ground at only one end (to prevent a ground loop) and not connect to pin 2 of V1. You can ground either end of the shielding but be sure that the other end is protected from touching anything, including the inner lead. Because they are easy to read, you can reference any Fender schematic (the Tweed era amps are really good for this) to get a clearer view how an input jack should be wired.