How could i make my engine better?

[Turbo Deuce]

Simple green is your best friend!
I assume you are pulling the engine. If so, clean the engine bay good and rattle can some gm satin black on it. Then if you change cams have the intake cleaned and clear powder coat it. Sand or media blast your headers and paint them with header paint.

Then when you install the engine take a day and plan your wiring to hide it or run it to where there are few wires showing. Buy the plug wire pieces to make them neat and route then under the headers if you can.

Run those trans lines under the engine to the radiator. Run the alternator wires between the intake and valve cover.

Vibration usually comes from the driveshaft. Make sure it is balanced and the yoke is far enough in the trans.

I am assuming that since it is a 400 the engine was internally balanced