Even if you found a year with similar dimensions, you'd likely face problems with:
* Seat mounting brackets: The floor mounting points and seatbelt anchor points are almost certainly different.
* Seat track compatibility: The tracks that allow the seat to slide fore and aft are unlikely to match.
* Wiring: Heated seats, power adjustments, airbags, and other electrical components will likely be incompatible.
In short: Don't expect a bolt-in solution. You'd need extensive fabrication work to make them fit, and the result might not be very safe or comfortable. It's generally much simpler and safer to find seats specifically designed for a 1999 Ford Ranger Extended Cab. Checking salvage yards or online parts suppliers for Ranger seats is your best bet.