Possible future mod. Good discussion here: https://forums.aaca.org/topic/260338-disc-brake-conversion-instructions/

Consensus is to use Scarebird brackets which permit use of generally available brake parts. I reviewed the parts list and attempted to find each part and cost it out.

Part	Cost	Link
Scarebird Bracket	$170	https://scarebird.com/index.php?route=product/product&product_id=51
Rotors	$45 x2 = $90	https://www.carid.com/raybestos/r-line-vented-front-brake-rotor-and-hub-assembly-mpn-5006r.html
Caliper – LH	$31.50	https://www.napaonline.com/en/p/ACASE4631
Caliper – RH	$31.50	https://www.napaonline.com/en/p/ACASE4630
Brake Hose	$20×2 = $40	https://www.napaonline.com/en/p/UBQ36797
Inner Bearing	$16×2 = $32	https://www.napaonline.com/en/p/BRGBR5
Outer Bearing	$16×2 = $32	https://www.napaonline.com/en/p/BRGBR3
Wheel Seal	$2×2 = $4	https://www.autozone.com/suspension-steering-tire-and-wheel/wheel-seal-front/duralast-cv-axle-seal-8871/12128_0_4988
Bearing Dust Cap	$4.50×2 = $9	https://www.autozone.com/suspension-steering-tire-and-wheel/wheel-bearing-dust-cap/dorman-wheel-bearing-dust-cap-13977/730036_855259_4222
Banjo Bolt	$5×2 = $10	https://www.napaonline.com/en/p/UBP82698
Pads	$46.50	https://www.autozone.com/brakes-and-traction-control/brake-pads/duralast-max-semi-metallic-brake-pads-dgc52msd/849483_1122062_25190
Master cylinder only	$80	https://www.carid.com/1967-buick-riviera-brake-parts/acdelco-professional-brake-master-cylinder-1496132393.html
Booster	$90	https://www.oreillyauto.com/detail/b/brakebest-brakes-4474/brake-systems-16456/brake-hydraulics-16513/power-brake-booster-11301/69bab478e25a/brakebest-power-brake-booster-remanufactured/5471324/4567655/1965/buick/riviera?pos=0
Total	$572	$662 including booster

However, one challenge is the existing front Rallye wheels aren’t going to fit properly with the disc brakes. It seems the best solution (for keeping Rallye wheels) is to find some front-disc wheels off 67-70 Riviera. The wheels are the same size, fitting the same hub. However, the center cap opening is larger but its possible to be repro center caps for the larger opening.

https://forums.aaca.org/topic/276988-65-rally-wheels-fitment-and-id/

Other alternative is to purchase new rims, but there seems to be a lot of calculations to do for back-spacing.