FoMoCo engineering got 'lit up' after the competitive tear down, where they viewed and priced the '61 Pontiac laid out on the table, with cost estimates for each part (and examples to drive in the lot.)
The difference between what Ford had just approved for '63-4 and what GM had in production was staggering; GM had lighter, faster, sleeker and better trimmed cars at a lower cost, but selling for a higher price. Rear end, meet sling.
To develop the 1965 Fords, engineers blew apart the '62 Pontiacs (which sold even better, and were winning everything in sight on the track) and used them as the basis for their mechanical prototypes. Some protos still wore full (or partial) GM sheet metal.
So.... if it looks the same, that's cos it started out the same.