Honda Civic 93' Engine/Interior

i recently cooked my civic's engine after a weeks racing and not paying attention to the massive crack in the radiator and had to purchase a reconditioned engine. its the same engine but since its been put in when my car idles the engine and and dash around the front passinger has began to rattle also in the first two gears or untill i hit around 60 Km/h. How can i tell if it is something as small as the bonnet being loose or if its something more important, i do most of my own work so if there is any particular thing i should check before having to return to the yard what would u recommend? also my car idles higher than it should i adjusted this myself and this rattle was not present before.

thanks chris