did you go on dyno or driving and tuning
i tried to find someone to tune mine ire in wisconsin and no shop wants to touch it because law about emissions
if your LC is 1991-1992 your tach wil not work with DD i do not remember exacly why but something with high woltage vs low voltage i have 1991 and i just instaled 1994 tach and it works no problem so you must use 1993 -1994 tack if i remember corectly you do not need to replace whole cluster...
well look at radiator from silverado truck it is almost double the size
i had extreme duty fan clutch and it was keeping the engine cool without a/c on with no problems , but on hwy and a/c on engine temperature will go over 230 F
but i did not like how loud was that fan
so my solution was...