Had a '96 GBM Cruise Master on a F53/460 and never had a vapor lock or downshifting issues. The original fuel pump had a design issue and was swapped out by the original owner within a year of purchase. The rig would lose power according to his shop bill. The new design pumps require a new wiring harness. If you did not replace the wiring harness, then you had the new pump design.
Did you make sure you had spark, before assuming it was a vapor lock? Ford was also known for control module problems. They would run once they cooled down.