somewhere in the main circuit from battery positive post to FL to bulkhead inside dash to ammeter to welded splice to bulkhead & out to alt there was a dead short to ground (plus from welded splice under dash it goes to the fuse box/steering col (ign sw)/headlight switch. everything is hot all the time like the wall sockets in your house which is why it smoked when you reinstalled the battery without turning anything on. it smoked under the hood so start by tracing from the battery to the firewall & see if you can decipher where/how it got shorted to ground. NAPA has new brass "Packard 56 type" 1/4" male/female terminals for 99 cents ea (725147/725145) tho with the bulkhead damage you may have to run em straight thru. I think you can have someone replace the damaged circuits but first we gotta find that dead short.