First off, you have a good battery I suppose. You have checked the cables? There are at least 3 maybe 4 wires (one from battery, one to starter and then two smaller wires, maybe have alternator wire also) on the solenoid on the fender? Are the wireds attached to the correct terminals on the solenoid? The starter has been checked and is good? The engine has a good ground wire from the block to the body?
Have you removed all the plugs and tried to turn the engine with a socket and breaker bar on the crankshaft bolt that holds the harmonic balancer on? Doess it turn freely?
Have you tried jumping the starter solenoid with a screwdriver from the small terminal to the battery terminal?