This is for the ender3 "v1", 4020 extrusion, with bed wheels that are not symmetrical (based on Creality CAD model of the ender3), I'm not sure if more recent bed have a different wheel pattern. As you can see the larger screws on top on the left side are not aligned with the screws on the right side (these would have been the wheel position)

linear rail was tricky on this, due to the bed undercarriage screws sitting right above the rail block optimal position. Requiring a bed lift (raised 6mm from stock), which creates a belt issue at either end of Y. So there is a new belt grabber that comes in play, I'm not sure this will work with stock belt, I would lean toward no.

The stock Y tensioner wouldn't allow the 300mm rail to be installed well, so has to be replaced with the Y tensioner I made to avoid collision and allow full 255mm Y movement and full 235mm printable space in Y. This has been tweaked from previous released model of the tensioner for ender3v1

Optional: Big motor mount for any size nema17 motor up to 60mm long, with an upgraded endstop to work with the rail setup. (stock motor mount with stock motor will still work fine, I have a smaller endstop mount for such setup), this definitely requires a longer belt than stock
