Given the amount machining needed, would it be possible to just remake the mounting plates so they fit the stock 9C1/impala hardware?
They too fit that stock aluminum wheel you pictured as that is the set up I have on the 91.
Granted, your present setup maybe easier for european members.
When referring to hardware, do you mean rotor, caliper & abutment? What about the park brake, which is why he made the caliper choice he did?
As you say, this setup may be more viable for Euro Caprice owners, but maybe some here would be interested in having the bracketry or drawings for them. I'm not sure there's enough demand for rear disc conversions that can't be supported by existing resources here in the US, at least for sedans. Wagons are little more challenging, but regardless, the change to rear discs is beneficial, and Vlad worked hard on his version (for sedans).
There could be some concern with caliper piston sizing vs the OEM disc setup, so it's not clear how this kit compensates for that. The rotor is larger than OEM, so the clamping point of the caliper would be further out, but as far as piston area and master cylinder sizing, it's probably not going to be the same as the JL9 discs....but those had their issues, too, with the stock proportioning keeping them from doing their "fair" share of the work.
Most of the time people here want something that is turn-key/bolt-on, with no or minimal machining or modification of the existing housing, axle shafts, etc. required. Rotor stud pattern & hub register are understood as "must have", but not everyone has easy access to a shop that can make those modification in a cost-effective or timely manner, so that can be a challenge.
- if you're confident in the viability of the kit development and want to offer something, you're going to have to think about shipping as an offset cost to what is currently available here. The other thing is that you want to come with a fully detailed installation, painted or plated parts, and list it in the Parts for Sale area, so people understand what you have to offer, and what the cost may be. The essential parts are the brackets....everything else is probably obtainable here, given the right part spec info. Shipping anything MORE than brackets (machined rotors, calipers, etc) would be cost-prohibitive, if I understand your location.