273 or 318?

Check on the passenger side of the block, on a machined pad just above the frame rail to see if it is your numbers matching engine. The machined pad is very close to the drain plug you can see on the side of the block. Last 6 numbers of your VIN will be stamped there if it's the numbers matching motor. You will have to jack it up and put jack stands under it to be able to do that. Too much work in that heat! Might have to wait for cooler weather....lol.