It is extremely easy to find parts for those models Chevrolet. They are really popular so reproduction and salvage parts are plentiful. However some parts are also very pricey.
The tri-five Chevys (55,56, and 57) are some of the most popular restoration project vehicles. There are a number of companies that specialize in reproduction parts for those models, so you should be relatively ok.
When a car is this old many parts you can not just get at regular car parts tores like autozone, so you have to sepcial order them online or through catalogs. So its not to hard to find them, but it does take time and patience.
It will be tough to find but in todays world there are many aftermarket parts manufacturers who produce quality replacement parts. Take a minute to search online for cheap parts.
