57Fury440 there is a lot of wrong information above.

The Street Demon is not spreadbore, and it will not work with the later 340 spreadbore intake that thermoquads came on. I believe its actually the primaries that bind on those intakes. If you in fact have the 1970 340 intake (four holes) it should work on that intake. The Street Demon pattern is much closer to the Holley 3 Barrel design, except the rear barrel butterfly is goggle shaped instead of an elongated oval. Its the "nose portion" cutout of the goggle that allows it to flip open on regular intakes, unlike the big oval holley three barrel which required a notch in the intake to accommodate it, this is why LD340's came from the factory with a notch between the secondaries.

Part of the Street Demons choke housing does hang a little below the rest of the base mounting surface. Its a small bit of the choke pull off mechanism so it MAY fit nicely into the intake's choke well, or at most you'll need a thick base gasket or a couple thin ones stacked together.

If you have a low profile air cleaner that can be a problem as the accelerator pump level sticks up above the top casting that same way a thermoquads does. On mine I had to cut a hole in the air cleaner there and tack in a little bubble to make clearance. If you are using a stock style air cleaner you are probably good to go. Just test fit everything as you go.

Hooking up linkage was a pain in the ass for me. The throttle lever pin they sell for the street demon, I couldn't even figure out how it was supposed to work. I ended up using a holley throttle lever adapter and a stock mopar pin/stud whatever you want to call it but had to drill a new hole in the adapter lever to get the overall throw of the lever to match up with the factory kickdown linkage.

While you are at it I would highly suggest ordering the tuning kit that has rods/springs/jets etc. Mine was super rich from the factory.

Be advised that the tiny little screws that hold down the metering rod springs are put on with loctite at the factory. Making them easy to snap if you aren't expecting them to be glued in. A tiny pencil torch from harbor freight to heat up just the area around the screw is useful.

Good luck!