‘67 Fish in Texas
Grab as much oem stuff as you can with the 383/727.
@4spdragtop is correct on this one. Grab EVERYTHING from the donor vehicle if at all possible. If it connects to the engine, take it with you. Hoses, wiring, kickdown, cables, etc. You'll probably want to get the radiator too.
Luckily, the 67-69 Barracuda came from the factory with a 383, so you are not re-inventing the wheel here. You can go here to download a couple of 67 Plymouth factory service manuals:
Service Manuals – MyMopar
I prefer a printed manual if it's available. I've used these guys for a number of FSM's and have been very happy with them. Here are their products for your car:
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There are plenty of resources available to you via the search engine, and many members who have done this. Good luck!