1980 Ford thunderbird with a 5.0 engine

I have a 1980 Ford thunderbird with a 5.0 engine, I have taken the engine out and have replaced almost everything new on it. Now I have put the engine back into the vehicle and have tried to start which is will not turn over. I took off the starter and had it tested it came back that the starter was bad so I have bought a new one and have put it in the vehicle. It still won't start.. I have replaced all the spark plugs and wires replaced the starter solenoid and tried starting and it still won't turn over. I have connection the battery is good had it tested the starter solenoid has power. I checked all the fuses I have no idea what else to check or what it could be. Please let me know what else to do or try to get this lowrider on the streets thank you Sonya