Go b18c2 if your budget can't go for c7. Later you can change cams and the gearbox or whatnot.

B18c to ek you need vtir loom and wire the vtec solenoid and knock sensor. You gotta change headers and cat to fit.

Legally you need eng cert to rego b18 to ek but sometimes depending on vicroads you can get away with it. Good luck. Ive asked before and the guy said as long it's a 4 cyl to 4cyl it should be ok. Shows how much they know