You can convert to 10" spindles, but they're not reproduced so you'd still have to find a set. And then buy the conversion kit on top of that.
You could also go to DoctorDiff, and buy a complete disk conversion from him. He sells the '73+ mopar based conversions, so it would all be factory reproduction parts. That kit can be had in either 5x4.5" or 5x4", although I'm pretty sure the 5x4" version still won't work with your factory SBP drum wheels because of the hub bore diameter. So you'd still need wheels. If you convert to 5x4.5" you'll have to decide if you want to do the rear axles too, which would then mean new rear brakes. So that adds up, but you'd have better brakes all the way around. Cass (DoctorDiff) is also super knowledgeable and can make sure you get everything you need.
DoctorDiff Drivetrain Components