I am swapping the 5.3L in my 1999 (late year) Silverado with a Gen IV 6.2L. I know I will probably use a new ECM for engine management and will convert the signal coming out of it for tach and speedo. The problem I have is the water temp and gas tank level both come through the Class 2 data bus and will not work with a new ECM. How do I get functionality for both of these gages (I want to keep my stock instrument cluster)? Can I leave the old ECM in just for gages?