First post, but I'm a long-time lurker!

I'm replacing rotten rear framerails on my '68 Charger, and a wise man on here suggested i may want to consider getting the metal and having them made up at an engineering shop.
Can anyone weigh in with their experiences doing this, in terms of the differences between having your own rails fabricated and buying a pair?
Any help is appreciated, as a bit of a greenhorn I've got a lot of learning to do.

Cheers,
Jack