Synchro, I have recently installed new cast iron brake drums and the Deluxe Dead Stop Brake Energizer Kit from Flathead Ted to enhance my mechanical brakes. I have 16x4 Kelsey Hayes wire wheels installed on my pickup with Firestone 650x16 Bias ply tyres.
https://www.cokertire.com/650-16-fir...blackwall.html
I installed the energizer kit and cast iron drums to the front first, as recommended by someone (cant remember who). I took the car for a drive and managed to lock up the front brakes/wheels without a problem.
I have also installed the kit and new drums to the rear of my pickup. All 4 wheels can now be locked up. My braking is now a huge improvement over what it once was.
I have adjusted my brakes so that the front brakes engage before the rear brakes.
I cannot say for sure that you will have the same outcome with radial tyres and a wider contact patch with the road, but this has been my recent experience with upgraded mechanical brakes.
Good luck with your brakes, regardless of which way you decide to go.