Prepare the jars. Wash the jars with hot, soapy water, place them in a water bath canner filled with water, and keep them hot. Wash the lids and rings and set aside.
Bag the pickling spice. Place the pickling spice in a spice bag or cheesecloth tied securely with kitchen string.
Make the brine. In a large pot, combine the remaining ¾ cup pickling salt, 8 cups water, spice bag, vinegar, and sugar. Bring to a boil over medium heat, stirring occasionally to dissolve the sugar and salt.
Simmer the brine. Once boiling, reduce the heat to medium low, cover, and boil gently for 15 minutes to infuse the spices into the liquid.
Drain the cucumbers. Transfer the cucumbers to a colander over the sink, rinse with cool running water, and drain thoroughly.
Pack the jars. Pack the hot jars with the cucumbers, leaving a generous ½ inch headspace.
Add the seasonings. To each jar, add 1 teaspoon mustard seeds, 2 fresh dill heads, 1 clove of garlic, and ¼ teaspoon pickle crisp, if using.
Fill with brine. Ladle the hot pickling liquid into each hot jar, covering the cucumbers and leaving a ½ inch headspace.
Remove air bubbles. Run a bubble remover or chopstick around each jar and add additional brine if needed to maintain proper headspace.
Seal the jars. Wipe the rims with a clean damp cloth, then apply the lids and rings until fingertip tight.
Process the jars. With at least one inch of water covering the jars, bring the water back to a full boil and process for 10 minutes, adjusting for your altitude if necessary.
Rest and cool. Turn off the heat, remove the canner lid, and let the jars rest in the canner for 5 minutes. Remove the jars to a heat safe surface and cool undisturbed for 12 to 24 hours.
Check the seals. Confirm each lid has sealed before storing.