I know how bad you want to find a match and I can appreciate that, but something to consider.
That year with 383 2 door how many were produced?? Usually half or less were four speeds.
Then look at the color. A little research will tell you the % of that year model were painted your color.
Then you take that number factor in the number of years since it was built, popularity for restoration, etc...and how many just like that are still out there??
You might have to reconsider the perfect match to Grandpa's car.
Something close may be your best option. You could always have it painted.
JMO