a trans with a non lockup can be converted back to run with a lockup converter , theres some mods made to the tranny to allow a non lockup converter to work and this needs to be changed back to allow a lockup converter to be installed , but even after the mod to the trans to return it to lockup the converter will also need to be lockup unit
i suppose its possible to take a non lockup converter and open it up and install clutch pack to make it lockup but the rebuild would be the same as if you were rebuilding a lockup converter , but you would need the internal parts and possiblbly a new front cover and i dont think it would be cost effective , better to sell the non lockup to someone looking for one and purchase a lockup converter