Helpful answer: OK here's a list, may not be complete:
New
Pedal box
Instrument fascia
heater box *
steering rack
steering column *
steering shaft
holes in firewall
dash liner *
grommets and bungs
wiring loom for the IP
throttle cable
brake booster
clutch cable or pipes
power steering hoses
brake pipes
*'d items are possibly OK
This assumes that the car was designed for both hand drives. If it wasn't than you may need to reroute the exhaust, move engine mounts and so on - it may just be too much work.
Off-topic, but when I was a kid I had a left-drive Hyundai Excel. The master cylinder was on the right side of the car, joined to the brake pedal by a big piece of pipe that rotated on a shaft.