Not really ' Custom" axles, but new ones. To have to the originals cut, and then you are stuck with stock. And to have them cut and replined correctly is about 250 bucks. You can get some for that depending on how many splines they are. 28 splines in Summit are like 220 from superior.
It's not pointless. You are not going to have a good shot at finding one that bolts in very easily, unless your name is D.Hearne. That damn guy has all the luck. PM, tell me what you have to spend, I know a guy out there about 20 miles away that has a 9in small bearing rear from a 67 shelby. It will bolt right in.