How to tell 340 vs 440

Small blocks are easy (as a rule) to ID

Look at the front of the block, under the head / deck parting line on the driver side. There will be a big long number there, and the CID will be in the first 4? or so numbers of that string.

The exception is some "crate" or rebuilt engines might have the number "x'd" out

Also there will be casting no's on the side of the block, driver side. This will also show the CID

The later small block magnum engines have different valve covers, vertical intake manifold bolts, but this is complicated by some guys adapting Magnum heads to older engines. If you have such a combo, either the seller "has to know" or you are faced with tearing it down and figuring out what you have.

There are other differences......................LOL