360 into 1966 valiant

Use the B&M flexplate 10239 to bolt up the convertor and maintain 360 external engine balance.
You'll need a crank flange reducer bushing for the convertor snout, they changed diameters over the years. Available through Pat Blais Transmissions or through several members here- I believe @Charrlie_S is one of them. Or just have a custom convertor built to accommodate the balance and snout issues.
You'll need a carb, manifold, and distributor for the 360. The '92 360 is factory TBI.
You'll need to space the driver's side 273 exhaust manifold (the truck driver's side manifold won't fit an A body) out from the head by using a bare header flange, there's interference issues between the head and manifold otherwise. Or else run headers.
you'll need a radiator with a passenger side inlet, they switched sides in '70. Or swap the 273 timing cover and water pump onto the 360.
The passenger side motor mount bracket will need to be modified to fit the 360- lots of threads on here about that. The driver's side bracket will need a 1/2" or so spacer between the rear engine block mount ear and the mount bracket.
You'll need a 360 passenger car oil pan, pickup, dipstick and tube to replace the truck parts on the 360.
And a bunch of little things, like throttle and kickdown linkages that will need to be modified.
It's not as difficult as it sounds, but it's not a "drop in".