In theory, K-jet can be retrofitted with D-jet. Not 100% sure on cylinder head compatibility but if not, you can take off the cylinder heads from the SLC and put them on the SL. Alternatively save time and effort by replacing the whole engine. Also, you'll have to change other components including fuel pump assembly, the D-jet computer and its wiring, etc. You may be better off getting a K-jet 450SE or something similar and sourcing an engine from that.