1965 Barracuda

Yes it will fit.
As far as swaps go, I did one of these in 1974 at age 21, knowing almost nothing about Mopars. I stuffed a 340 into a 65 Valiant Wagon V100, that previously had a smoking slanty in it.. Smoking as in add oil twice a day. lol

Here's what I know;
yes the engine will bolt in with a car oilpan.
with any 904-based auto trans
with the 273 engine mounts, and the
65 trans x-member, and
With the 273 logs.

Before you start, for whatever trans you intend to use, make sure the convertor pilot fits snugly in your crank, and if it doesn't; take the appropriate action to mate them up..