What extruder & board would you use for a Frankenprinter?

Got a CR 10 Smart (spoiler alert: it’s not.) for free and I’m planning on using it for concrete molds. The quality doesn’t have to be the bet, but I do need it to work reliably. That means that the stock board and extruded need to be binned and replaced.

Which extruder and board would you personally recommend? I’m familiar with Klipper, and fine with fiddling a tweaking to make it work, I just need recommendations for the hardware.