Im lookin to sell a 1965 GT mustang. where do i find the serial numbers on the engine and tranny?
Ford didn't put individual serial numbers on their engines and transmissions. You will need to research the VIN of the car to find what engine was specified (e.g. 5th digit of the VIN would be a "K" code for a high performance 289). The engine block and tranny housing have casting numbers that can be related to the year and sometimes model of the car. When someone refers to a "numbers-matching" car, it means simply that the car has a drivetrain that is the correct vintage and specification for that car, not necessarily the original engine/trans.
Get a book on 65 Mustangs that has the decoding info for the various components, that is your best place to start. Any original paperwork (bill of sale, dealer invoice, build sheets, maintenance history, pictures, etc) all can increase the value of the car.