Electric problem

[Randy59]

I have a 95 chevy swb pickup 350 v8 5speed Trans. I've replaced wiring harness with one from a 84 chevy pickup. I just had the clutch and flywheel replaced. Everything was working good except flywheel was broke. Now I have a problem with my truck starting. Battery voltage reads 12.56 volts but when I try to start it the voltage gauge reads 5 volt and my headlights come on as soon as I turn key on need help

 

[brianmcb]

Run a ground wire from your engine block to frame

95 rcsb, L33 5.3, hot cam, frost tune, 5spd, 4/6

 

[Randy59]

I did have one will check to make sure it's still there thanks