I am not familiar with the small block mopar engines but are there any external differences between them that can make identifiying them easier. Do they have an engine ID pad somewhere that tells you this?

Casting number on the driver's side of the block, 273, 318, 340 or 360 in the number.

Stamped number on the front of the block right below the driver's side head surface also.

360 balancer is easy to spot

CID is coded into the stamped no. just below the front of the drivers side head

If you look at a pan from a 318/340, the front/rear "half moon" cutouts are about the same size

Rear of 360 pan cutout is larger--larger rear main/ seal

I was thinking that the space between the motor mount lugs on each side of the block are spaced different between the 318 & the 360. iirc same spacing distance between the lugs on the dr side & the pass side if it's a 318, different distances if it's a 360.