you can convert the Capri 2.8 rear from drums to discs, but there’s no single off‑the‑shelf P100 kit; people use donor hubs/calipers or bespoke kits. Common routes: fit Sierra/Capri disc hubs and calipers (matching bolt pattern/spline), use a drum‑in‑hat or caliper with integrated parking brake, or get a fabricated bracket and rotor assembly from a specialist. You’ll need correct bearings, handbrake linkages or a separate parking brake, new lines and possibly a proportioning valve. Measure flange bolt pattern, spline count and axle diameter, post some photos and I can suggest specific donor parts.