My light alloy projects wouldn't be anywhere without HeliCoils- lots and lots of 'em, along with many many rolled-thread fasteners.
BasemenBorn- ARP folks say they will make any custom fastener; but I don't know how pricey that would be.
Very pricey. They make a lot of custom stuff for F1 and Nascar, and have learned how to charge for one offs . . . . . . .
Financially, you are way better off adapting something from their normal stock, to work for your application.
But hey, if you can afford to have them fab up something special, by all means do so.
My point is this: Both ways work.
My advice is: Don't get "hung up" on your project, looking for the "
perfect" solution, if it doesn't already exist. Adequate and/or acceptable are not "bad words", and they get the job done.
Fordboy