Rebuilt motor 95 Jimmy Won't Start

Rebuilt motor. Bottom end. Reinstalled motor. Made all electrical connections,but have no electric to interior lights, headlights. When
key is turned, nothing happens.Fuses were checked and are fine. The
only area that has electric is the starter.
Any help?
1995 GMC 4.3 Vortec 4x4

Welcome to AF.
Check for power to fuse block.
Check for 12 volt to back of alternator and on to fuse block.
There may be a fuse link between alt to fuse block and make sure you got all power feed wires on back of alternator back on it.
And all grounds wire backs back on engine and battery..

Thanks for your help...the actual problem was a crossed wire on the starter.
Now it starts, but it backfires horribly!:confused: