My computer went out and I got everything wired up except the Speedo I ran the wires one from vss and other to ground can’t remember what colors right now and now it won’t read the right speed and the needle bounces like from 20 to 60 constantly if the truck is moving and I put a new vss on to

 

Also if it helps my odometer gears are broken so my odometer doesn't work

 

VSS units come in different gearing. getting a different one will change your speedo reading.

You can use it to your advantage like using a 3.5 gear VSS in a truck with 4.1 gearing, with 37-40 inch tall tires to get the speedo very close to reading correctly. I have done that before several times.

Just randomly replacing VSS units will get you random changes to your speed reading.

It sounds like you have a '92/'93 which runs off a electrical signal for your speedo to work. If it bounces as you describe, it likely due to a bad connection, broken wire or ground.