After a hugely successful first season for its new “sports car,” Ford saw fit to change the Thunderbird only slightly for 1956. The optional removable hardtop was now fitted with round rear quarter-windows, soon to be dubbed “portholes” by enthusiasts, which were intended to increase rearward visibility for the driver. Customer complaints about the spare taking up too much room in the trunk were answered with a rear-mounted one, which was a variation on the Continental kit that…