440 swap on slant six 73 duster

Start with a mild big block. Easier to add power as you add years of driving experience. The placement of the engine starts with the transmission mount. If you don't already know, Mopars have the engine offset to the passenger side. Use the same offset you measure at the trans mount and use that for the front of the engine. Crank snout should be about 5-1/2" above the lip of the k-member. You can make mounts or a motor plate from there. Once one thing is done you will have more questions. Keep on asking.