I have Mortgage Lifter seeds. My growing season is too short for them it seems. Here at 8,500 ft in the Colorado Rockies we only have about 90 days between frosts. I have to start indoors several months early for many things. Potatoes do very well however.
Try some of the siberian, Alaskan and russian varieties. They were designed for colder seasons. I grow them in the late fall and winter here. No freezes in the San Fernando Valley. They grow well, quickly and are very hardy. Do a google search on Tomatoes for Cooler weather.