Probably the dumbest idea ever

So I have a 1965 Newport 4-door, as per the status quo it has the 383 in it. I was wondering (yes even after searching many resources) how difficult it would be to swap in a built 318 and trans??? (it will still be a 727 btw but a 1976 set up for a small block instead of the twin pump from 1965) I know there is some mounting boss difference on the engine mounts from 62(?)through 65 than from 66 on but is that a big deal to the point that some other type of mount couldn't be fabricated???
Author: Grease556