I got a stupid question

Bad Sport said
Look on the front of the block right under the driver side head. You should see some numbers "stamped" not cast right there.

It will be a series of numbers, but you should see 318 - 340 - 360 somewhere in that series of numbers.

A lot easier to get to.

This is the quickest and easiest for me "most of the time" but I have a "Mopar manufactured" engine on which that number was destroyed. "X'd out"

Another way is to acquaint yourself with the pan differences on LA engines.......everything except 360 has the LARGE "moon" at rear of the pan, nearly as big as the front. A 360 has a much smaller rear pan "moon"

And......look at the balancer. 360s' have a huge "off balance" around the balancer, others don't.

Other than that...........as above.........look on the side of the block for casting nu's. These are sometimes difficult. My recollection is that a 340 is hidden by the manifold / starter / head pipe "pretty well."

Here's a good thread

http://www.forabodiesonly.com/mopar/showthread.php?t=285021

Here's the stamping BS and I are referring to, and that's no "bs"

An example number from above

Pan rail after 68, pass side

Casting no. drivers side