The Banker, my wife has given the ok to buy a set of mag wheels for our 74 super, apart from buying over seas, who stocks them here in Australia. I what good quality chrome rims if I can find any.

OK - be very very carefull

as a 74 Super I "assume" you mean a curved screen??

Before you go outlaying good money are you going to lower the car at all??

Supers can look funny with new shoes if the rear is sagging and the front high

MOST IMPORTANT
check the offset of your new wheels

Stock is 4.5" with an offset (ET) of 41
Sports wheels were available in 5.5" with 26 ET

Most chrome wheels are of the "mangel" variety and have a very poor offset.
They stick out too far and will rub - even in stock height, let alone if you decide to lower

They are also of pretty poor chrome. If you park outside they WILL rust

You also need to be carefull / mindfull of your guards.
If you have originals that are undamaged - good.
Cheap copies are all over the place in shape and cause rubbing problems.

Use this programme to compar different offsets
http://www.1010tires.com/WheelOffsetCalculator.asp