Not an easy question to answer. In fact, after checking many older cookbooks, we eventually turned to what should have been one of our first choices, Alice Arndt’s excellent Seasoning Savvy. She says older cookbooks, especially British or Australian, sometimes call for mixed spices, and various mixtures used to be sold by that name or as French spice or spice parisienne.
The spices used in these mixtures were the "sweet, warm favorites of English cooking, of the sort that make up the pumpkin pie spice blends in the supermarket today," Arndt says. Mixed spices are quite likely to include allspice, cinnamon, clove, coriander, ginger and nutmeg. You might be quite satisfied using pumpkin pie spice rather than putting together a mixture of your own.
the same time, a number of the chow-chow recipes we’ve looked at – none of which appear to be British or Australian – pretty uniformly call for dry mustard, ground turmeric, and celery seed in the spice category. A couple add allspice and one also calls for clove. So it appears there has been a trend away from the sweet, warm English spices for green tomato relish since your recipe was written.
But as we so often find, a new recipe is not necessarily a better recipe. Here's another option: Leesburg ChowChow