new dash

ok guys here it is...im stuck in finding a way to get the dash cluster to work with the new engine. what i need to know is if i find a ls1 dash set up the entire dash with cluster and replace it with the old one. i was already told that i would run into trouble getting the speedo and tacks working correctly because how they are set up in 3.8's. so if anyone has ever done this or know of a person who has done this and how please get back to me on this. thanks