It depends a lot on where you are (east or west coast etc) and what you want. Buddying up with someone to split shipping is always a good move.
AzCoupe has a good reliable contact in Melbourne, Australia. He is well-connected to the Ford wreckers in that state, and can get most things pretty consistently, and of good quality. There are also the part-time exporters such as aussiexports and Ausford.
With any purchase, there should be a stipulated timeframe for delivery. Remember too, that installing and finessing the motor transplant consumes good amounts of money. Purchase and freight are only two elements of total cost in a swap.