VTEC motor going in to a non-VTEC chassis takes more work/wiring than non-VTEC going into a VTEC chassis.
And if either of these are you scenario....you need the replacement motor's ECU too.
But the work can be easier if you can take the engine harness off the motor and maybe even the harness from shock tower to cabin can be scalped for VTEC wires. Thy can be pinned into the other harness so VTEC wiring will be clean, simple, and solid.
Ffsquad.net has some great pictures and such when it comes to taking wires out of plugs. Simple jeweler's flat head works well.
Please give more detailed info on the motor and ECU's you currently have. Motor's info is near the radiator where motor attaches to the trans. ECU.....letter/numbers in the middle of the bar code.