70 Duster--conv. to 73-76 front disc??
Whether the KH brakes will stop it or not he is right about cost and availability of those rotors and pads in long term. The spindles for 9 or 10 inch drums can be found cheap enough and the normal wear parts used in the Scarebird conversion "should" be affordable and available for many years to come.
There are many K-H equipped cars still on the road, and the prices are exactly what I quoted in the earlier post, $39.99 for Centric rotors. Summit is selling these rotors in slotted/drilled form for $79.99. Caliper parts are widely available. Stainless sleeves can be installed to solve any rust issues in the piston bore, as a lifetime upgrade. Overall the cost to convert to any brake system is going to be a lot more costly even over time, then sticking with a good, highly effective K-H system with the SBC wheels.
Sticking with the factory K-H setup avoids the expense with swapping rear axles (re-drilling existing rear drum bolt patterns is a potential safety issue), the wheels and picking up either aftermarket pieces or the '73-'76 setup.
When you add up all those expenses, the change to the BBC is not cheap.
Unless the car is a daily driver getting really hard usage, the rotors should last, and can be turned at least once. Given how many use these cars, mostly for weekend events, you can buy a couple pairs of rotors for future usage.
A couple of buddies of mine are running 416 or 408 strokers with the factory K-H setup and the brakes haul the cars down at the end of the 1/4.
All I'm saying is look at the total expenses with any conversion; the costs can mount up quickly.