My parents have a ranch style house with a 3.5 ton, 13 seer heat pump (R22). The house was built new ten years ago. The condenser coil has developed an unrepairable leak and needs replaced. The issue is now that the installer sold them a possible stolen unit. All the identification numbers are removed. There are no tags on it anywhere. The company that did the work is no longer in business. We are being told there is no way to match parts up without having the exact serial number and model number. Also being told that a Carrier or Tappan unit will interchange, but nothing else. Is this really the case? I can buy a Trane unit today, but there's no point if it won't work I know eventually we will have to do a 410a change over, but they can't afford a $4k+ repair right now. So, is there any way to either find the numbers on the existing pump, or can we mismatch (with possible reduced efficiency), or do I have to find one of the three brands? Thank you for your help

This is an odd question and I may be an idiot for asking. But was thinking there are hundreds of thousands of Condo complexes with in wall sleeve ac units (like me) that would love the improved acoustics and air flow from a ceiling or high on wall mounted split unit but that cannot affect the 'look and feel' of the exterior of the building. To that end is there a reason a nobody offers a condenser unit that would fit in the existing sleeve with an acoustic access panel on the interior and then pipe up the 8-9ft in the wall frame to a ductless split. Result would be a much quieter condo with a more efficient ac and no chance to the look and feed from the outside. Either a) I am and idiot because it cant work or, b) it already exists, or c) I have had a brilliant idea and should quit my job and head to silicon valley right now. Just curious.