For the trim gauge check the trim sender on the side of the gimbal ring, these are know for broken wires. If they are broken replace the senders when the bellows are done next time.
Regarding the speedo chech that the tube is connected to the drive fitting. Front between where the Rams attach, kind of back in a cavity.
1997 2400 SCR
5.7 Vortec / Bravo 2