For B-series, the EK is one of the easiest Hondas to swap. The EM1 already has B-series mounts, so dropping a B18C1 or B18C5 into any EK hatch or coupe is well-documented. Mounts, axles, shift linkage, and ECU harness kits exist from multiple aftermarket sources. K-series swaps are more involved. You need swap mounts, a custom or adapter harness, modified shifter setup, and usually a K-series compatible ECU. Both swaps are proven and thousands of builds deep at this point.