My 1972 Ford Thunderbird has no power, no electricity even after I've replaced it with a brand new battery and installed a new alternator???

Sounds like bad/dirty negative battery connections on the frame and motor.

With it working with a jump start i am almost positive that it just a connection issue somewhere. I would also tighten and clean both battery connections on battery. If the connections are old and tightened all the way they can go I would replace them. Also look for corrosion on the wires to the terminals. For giggles you can take the jumper cables and only connect the negative cable to your battery and the other end of negative to good metal on the motor. If power then is restored the problem is with the negative battery connections either on battery or frame/motor.

I found on my 65 that the cable was only making contact with one tiny wire within the whole cable! It looked good and when I tried to move it, it still held but was not heavy enough to let power pass. I would advise you to check your battery cables (pos and neg) by taking them off the care and do a good inspection.