Thanks to some info from here, and some mouse work have come to conclusion i have a 318 poly, can anyone tell me what it is most likely to have for a transmission and rear gears, if still factory.  

if its a automatic it a 727 torkflite ,not sure on the rear...  

My '66 has the 318 Poly 2BBL, 727 TF, 8 3/4 rear end with factory 2.76 Sure Grip differential.

This was the standard setup for the Coronet 440 2 door hardtop with a 318 2 barrel from the factory.

Nice, easy running highway gearing- no tire smoking here at least in stock trim.

Get under there, and you should see a little metal tag with the gear ratio stamped on it hanging off the axel housing.

BTW, I've seen these original metal tags going for $20-$30 at the bigger swap meets, so don't be surprised it is missing.