Engine is very reliable, although the carb (Ford's VV) is not the best, you could fit a Weber. It's basically a revision of the Kent engine, revised to suit the Fiesta's drivetrain. Yours must be an early MK1, as they did not have servo assistance?

From circa 82 onwards electronic ignition was standard.

The same engine was fitted to the MK2 and even MK3 (although it was revised and called the HCS) which evolved in itself to become the Endura-E as fitted to the original KA.

The 1400 is the CVH engine.

The 2L Zetec is an easy engine conversion, but not what you are looking for.

Not sure on the brakes, as you say the wheels are the main limiting factor, they are also 'hubbed' drums.

Martin