Drum Brakes for front

Seems like a waste of time to swap the rear to me. Since you have a '74, you should already have the big ball joint UCA's in the front. Which means that all you need for the disk brake swap is the 73+ disk spindles, caliper brackets, rotors, calipers, disk master cylinder and prop valve. The UCA's are usually the hardest thing to find and most expensive, and you already have them.

Disks aren't just for race cars. Even the 10" front drums on these cars aren't that great for stopping power. The worst part about the 10" front drums though is that you can't get them. No one is currently reproducing the drums themselves, so you're on borrowed time. As soon as you need new drums, you'll either be 1. Out of luck, or 2. Spending a ton of money for someone's old 10" drums. And if you go with #2, you're just on borrowed time again. Not that many folks are throwing away the 10" drums anymore, because it's getting around that no one makes them. Prices online have gone up for them, and anything that is getting junked is probably too thin to turn anyway.

You should even be able to sell your current drum spindles for a decent chunk of money. The large ball joint 10" drum spindles are what is needed to do the 11.75" rotor/viper caliper conversion that Dr. Diff sells, as well as a few other aftermarket conversions. You could probably get half the money for new disk spindles out of the old drum spindles.

And then you wouldn't be limited to the half dozen wheel options that still come in SBP.

Just my .02.