Correct 5 3/4" size
Two prong connector
This H5001 bulb is the closest Halogen Reproduction of the original FoMoCo headlight that we carry. This bulb has the number 1 at twelve o'clock (to indicate its position in the grill) just like the original, and the FoMoCo logo is actually formed into the glass rather that being etched onto it, as is on some other repros. This high beam is definitely going to be brighter than your original dim bulbs.
Note: Other than Cougars, only 1969 Mustangs used these bulbs.
Don't forget that you need to install a headlight relay kit when you install Halogen bulbs! Get em here:
67 - 68 relay
69 - 73 relay