Welcome - since your question is not really year specific I'll leave it here
i am new on this forum ! i am restoring a 68 fastback ! built in Dearborn on April 16.
what is the best paint to match my 289 engine ?
I would use PPG if you can still purchase and use it where your located
Ditzler DAR 13358 acrylic enamel
Mix it with some DXR 80 Delthane Ultra Urethane Hardener and somewhere between 15-20% Ditzler DX 265 All Purpose Flatting Base,Less than 20% flattener
8 parts color + 6 parts reducer (DTR 601 or 602) depending on weather etc + 1 part DXR 80-then DX 265 flatter
The search feature is your friend
http://www.concoursmustang.com/forum/index.php?topic=2282.msg11834#msg11834and what is the best paint for my engine bay ?
The issue here is that what is legal to spray, purchase and use depends on where your located. Without those restrictions I would say a catalysed enamel with lead would work fine. Of course your likely not going to be able to purchase it in your area.
Using the search feature should turn up many earlier threads and other members responses such as
http://www.concoursmustang.com/forum/index.php?topic=7852.msg44961#msg44961Remember to check threads for discussions on how the engine compartment black transitions to the body color along the top of the inner fenders