I have a 96 MC LS with a 3.1. The engine recently started knocking. I just happened to run across a wrecked 95 MC Z34 with a 3.4. Does anyone know if they will interchange?

The 3.1 and 3.4 are basicly the same engine except .3 more litres.. im pretty sure its a direct swap and you'd be done, I know that its atleast that way for Camaros.

The Lumina/Monte Carlo 3.4 is a DOHC, the 3.1 is an OHV. This swap would require a complete ECM, under hood wiring harness, as well a mounts, etc... to be done. I would look for another 3.1 to put in it, as the 3.4 DOHC is a big, problematic, tempermental, headache. Since your MC is a 96, it is definitely OBD-II, and the 95 could be an OBD-I hybrid, or an OBD-II, just one more thing in a list that makes this swap not worth doing.

Thank You very much for the help