I have a Lenovo Thinkserver TS130 which has some interesting HD carriages (the blue plastic part). I wanted to install an SSD but of course, an SSD is much smaller than a 3.5" internal HD. So I printed up an adapter (in red) to work with the Lenovo HD carriage. The SSD is bolted to the adapters, and then pins in the carriage line up with the holes at the very ends of the adapter.
I will say that instead of making the SSD centered in the carriage, it would be better if it was shifted toward the end where the cables are plugged in. But this works and it is obviously a really niche sort of item, so it wasn't worth it to me to do a whole redesign. For anyone who wants to make that change, or if you find the holes don't match up to your specific SSD, I have included the freeCAD source to make modification of the design easier.
Printed in eSun PETG, 0.2 mm layer height, on a Lulzbot Mini with a 0.4 mm diameter nozzle. With the stock 0.5 mm nozzle, I would expect the screw holes to be smaller than optimal and may require reaming.