Some confusion a j the cars vin says 273 but the block says 318 so not original .
That was my point a few posts back.
The 318 was not offered in the Valiant in 67, it came in 68 and later.
Your VIN number indicates that your car originally came with a 273, so someone has changed it at some time. Now we need to establish what year it is from.
Here's a thread on how to id your block/engine:
http://www.forabodiesonly.com/mopar/showthread.php?t=285021