The drive train on the Cadillac and Olds front wheel drive full size cars of this period up till 1976 were very reliable the trans is based on TH 400 which is among best transmissions. As long as US car companies made big cars the drive trains were good when they downsized they were in trouble. The CV joints are listed at Advance Auto parts for around $60 which I do not consider expensive.
Finding trim and body parts may be a larger problem and the Plastic pcs between body and bumper if original will be cracked or missing but fiberglass replacements are available.
Gas consumption is not a strong point. But in my opinion gas is not a issue on any old car small part of ownership of old cars.
Look at Hemming Classic car Magazine for some good articles on restoring or the cost of parts for the cars of the 60 - 80 a great mag for car people.

I second Randy comment on admitting to your mistakes> I know I have made more than I care to remember. As I was told when younger if you haven't made any mistakes you haven't done anything. Mistakes are part of learning. If you pass on your errors and post them here someone else can be saved the same or similar. Takes a big man to admit to small mistakes

Well then its happy birthday to Mr Rusty McPackard

My Memory of car dealer parts books were that they were about three feet long or more. This was before computer or micro film versions I think the term was micro-fish. The books I remember which were from local dealers which were also gas stations. These books were the hole punch type with long rods holding them together. I can remember going to some dealers later and asking for old parts and the dealer would have to go look at the old book rather than the new microfilm or computer screen to see what the part number was. This was the day of the dealer ships which were something and son or something brothers. Guess this dates me but the old time guys would a least look for a part now all they say is that's to old we don't have it and can't get it.

I have the Studebaker and the supplement for 1957 Packard Clipper which I will send to you to copy. It does not come apart like the regular manuals but is only 46 pages. The regular 1956 Studebaker manual is needed for some things it is the if you want to copy the Studebaker manual I can also send that but its a larger book similar to other manuals. The Studebaker manual cover the 352 Sky Power and the Ultramatic transmission. Not to upset anyone but both of these manuals are mark Studebaker Packard Corp.

If it were me I would get a nice box put them in there with the fuzzy dice, baby shoes, fox tails, mud flaps with lights, mark box do not open until I die and seal it keep in trunk. As you may have guessed I do not care for them but its your car do what makes you happy.
This seems to be a touchy subject

Not a real animal but we have a Turkey on the site thanks to BigKev Good Job ti's the season to eat in excess ask the man who does.

I know of one 1957 Packard that was purchased new with a 1950 Packard for a trade which he received $800 against the new 1957 Clipper $4353.38 price. This car was sold about 3 miles from the dealer where it was kept by the first owner and his wife.
When the Husband died the widow had a young man up the street drive her around in the car when she died in 1987 he got the car.
When the fellow died his father kept the car in his garage for two years father put it up for sale two that is when I came into the picture being the third owner of a 1957 Packard with 30000 miles and only a small amount of rust on a Pittsburgh car which is in it self hard to believe. It has been my dream since 1957 to own a black 57 Packard. Now to get it back to the way I remember them when new .

check this link about Packard PT engineshttp://www.ptboats.org/20-01-05-ptboat-008.html
Also this onehttp://www.pt-boat.com/packard/packard.html

McMaster-Carr has it by the foot in various sizes great people to deal with have many hardware parts used on cars have excellent on line catalog see page 209. They have fast delivery and not high shipping charges .Not sure of shipping price to you guys down under.