318\a904 swap in 65 barracuda

Okay, LOTS of threads on this; search function is your friend. That being said, here's the basics:
ENGINE & TRANS
If you've got the D150 that you're pulling it out of, pull EVERYTHING you can; ie throttle cable, kickdown linkages, ignition and charging system wiring and modules, trans linkages and cooling lines, motor mounts and brackets, solenoids and battery cables, ground straps, the works... you may not end up using it all, but the way these projects go, more often than not you'll be glad you've got it. Don't forget to grab the driveshaft too, you might be able to get it cut down to fit your car; if not, you'll still at least need the transmission yoke.
Parts you'll need to source elsewhere: Passenger car oil pan & pump pickup, early A throttle pedal and cable (although you might be able to adapt the truck ones), and a '70-'76 A body 24" smallblock radiator and shroud and matching fan.
You'll need motor mounts and engine brackets for an early A V8. Or, depending on your abilities and creativity, build your own or modify the truck units to work.
You didn't say if you've got power steering or not; if you do, most truck power steering will hit the early A k frame. You can either source passcar brackets or shorten and redrill the truck brackets (about 1 1/4 in. if memory serves). I prefer to mod the truck brackets, that way I can still use all the original pulleys.
You also need a plan for your exhaust- if you have power steering, you basically have one choice: the early A smallblock manifolds. BUT BEWARE! With your '87 motor, you have air injection ports below the exhaust ports that need to be plugged (search the thread under smallblock motors). After you do that, you'll find that the extended pad beneath the #7 port prevents the manifold from properly seating. A little judicious grinding with a Dremel USUALLY takes care of it, but go SLOWLY! If you take too much, or core shift is really bad, you run the risk of breaking into a coolant passage, and you've got a junk head on your hands (go ahead, ask me how I know...). At a minimum, you'll need the driver's side manifold- the truck manifold can work on the passenger side.
If you have manual steering, that opens up a LOT of other options beside the early A manifolds: ANY standard A manifolds of any year (318, 340, 360), the 340 HP manifolds, or Ram/Dakota magnum manifolds, among others. All these options seem to require cutting back the collar on the steering column (again, use Search to get the whole story) and a little grinding on the manifolds for column clearance. And again, test fit the manifolds- some of these options also require grinding the heads for proper fitment as above.
If you want headers, it's Doug's, TTI, modded shorties (search), Spitfire fenderwell exits, or build your own.
On your trans, some of the truck 904s had cast-in reinforcement ribs that interfere with the extremely narrow transmission tunnel and crossmember in early As. You will have to grind these down to get it to fit.
Your year trans MAY use a speed sensor- if so, it needs to be replaced with a standard cable drive. Use a '66 cable to hook it up to your speedometer.
Reuse the truck cooler lines if they're any good. Just cut to fit and reflare.
Shift linkage is up to you. Aftermarket floor shifter, swap in a '66 non-cable shift column and linkage, or some other column and cobble up the truck linkage to it.

BRAKES and SUSPENSION
As mentioned, 9" brakes ain't gonna cut it in 2020.
If you're really bucks down, at a minimum, you could swap on a set of 10" drums and spindles, lots of guys who have upgraded to discs have these laying around and you can score a good deal. Otherwise, search the braking threads on disc upgrades and pick your poison. Lots of choices out there.
One thing to consider: if that year D150 still has the 4.5" bolt circle, grab the rear drums and backing plates in case you ever upgrade to the large bolt pattern. You'll be glad you did, or you can resell or use for tradebait on something else.
Same goes for suspension. At a minimum get some V8 T-bars in there and some good shocks. New rear leaves have gotten pretty affordable of late, it's not worth messing with saggy 55 year old units. Use Search and pick a vendor.
You may or may not need a different steering center link for the V8. Some slant 6 cars came with the V8 center link. Some guys have pulled off the swap without having to change theirs. Once the motor is in, see what you've got for clearance and make the call.
The rear end is dicey at best- non suregrip 7.25s like to grenade under raised power levels. Plan for a future upgrade. Some guys have lived with them for years, some guys never made it out of the driveway. Make your choice, take your chance.
As far as the driveshaft goes, one from a '66 Barracuda or Valiant
with a 904 should be a bolt in, if you can't find one, have the truck shaft shortened (provided it uses the right size U-joints for your rear). Have a new shaft made when you upgrade your rear.
ELECTRICAL
Use the truck harness to upgrade to electronic ignition and and better alternator and electronic voltage regulator. Search the electrical threads to find the modified wiring diagrams/schematics.

I'm sure I'm forgetting something, but this should be enough to get you started. Besides, my fingers are getting tired.
Tim