Poofff

Rewired whole car (68 cuda) as per factory manual.
Dash is still original. New solinoid, new starter relay etc.
Went to hook up battery and POOFF.
There was a pop, like a light bulb exploding from somewere
under dash and there was a faint burning odour. Also the starter relay got really hot.
Everything is dead.
Were do i start to find problem.