1/2 conversion problems

alright i need help on any of these matters that you think you may be able to help me with. i have a 97 truck with a 97 wiring harness and a 96 motor and 98 tranny, oh yeah the ecm is a 96. all of the harness plugged in except for the tach, i had already installed the tach and had the motor in the truck when i found out a 96 harness was not going to work and switched to a 97 harness, well the plug ins were different for the tach so i just cut the end off of the 96 harness and spliced it in on the 97. now, the speedometer doesn't work, the tach doesn't work, the alternator is only charging 12 volts, and my overdrive button on the dash doesn't light up to turn overdrive on/off, and the tranny won't shift. when it is in drive the truck takes off in 3rd i am guessing because if i pull it down to first it feels like it is taking off in 2nd not first, and then i can shift up to 3rd. anyway, just wondering if i need a 97 ecm or if anybody has had any of these problems. thanks for any help. oh yeah, oil pressure seems to be working fine as does the fuel gauge and the batt volt gauge as it is reading 12 volts which is what i was reading under the hood, and the water temp seems to be reading right but may be off a little.

Alternator won't work correctly without tach signal.

ok thanks, any reason i shouldn't have tach signal or anyway of checking?

ok so i ended up having the crank sensor to far away from the balancer, anyway that fixed everything but the speedometer and odometer. any ideas there, i put a new sensor in the back of the tranny with a new gear but it isn't working. also, i don't think it is shifting into overdrive but i haven't driven it very far.