Firedome, here is what I can tell you; The blocks, LA and A may be the same size dimensionally but not after you add the poly's heads. Not all the internal parts are interchangeable. Intake manifolds, cylinder heads, (obviously valve covers) and for the most part camshafts do not interchange. I had to have a cam custom ground (ISKY) for mine, and I was able to locate a Weind 4bbl intake. If I could take a picture of the 2 bbl intake manifold, you'd see how much wider the poly intake is over the LA. The 318 Poly's valve location is different from that of the LA engine family. The intake valve is on one side of the rocker shaft and the exhaust valve on the other side whereas on the LA engines they are located on the same side. This is why the pushrods on the 318 poly are a straight line from the lifters to the rocker arms but angled on the LA engines. What I was trying to communicate to you was the cubic inches are the same but they are not the same motor and maybe, there might be some differences as far as motor mounts, height of engine, and so forth. I don't know that for sure because I went from the 318 poly to a 440 not an LA engine. My concern would be for the "noise" the engine makes. These engines had a reputation for being very tough, used in trucks, and reliable. I suspect mine bit the dust because the Chrysler dealer that rebuilt it did something wrong. It ran hot before the rebuild and even hotter after. Usually it did not boil but stayed close all the time. I took it to a place near where I work and they had it for months and found nothing wrong. I took it home and water shot out of the dual exhaust. They said it was condensation. It was more like a garden hose. A buddy and me took the valve covers off to adjust the valves and green radiator fluid shot up through the push rod holes. Oops. I had quite a lot of money sunk into it (I had a custom bracket made to switch it to a 4 bbl, cam, inake, carb, other work) and decided to pass on fixing it. I sold the cam, intake, carb, bracket, and so forth. We found radiator fluid under the intake, on top of the pistons, and on top of the oil in the oil pan. The heads and block could have been cracked, blown head gasket, etc.. but it was cheaper to buy a 440 ot of a Super Bee that ran good and swap them in place. Again, I was only suggesting you make some measurements and research this before the swap is all. Good luck and I hope it turns out well. My engine ran strong with the minor mods.