Will a serpentine belt system and a.c. compressor from a newer vehicle like a dodge truck fit onto a 74 charger with a 360? Thanks.

it isn't a bolt on if that is what you are thinking.
take a 5.2 or 5.9 mag motor, trying to use the front on a 360 doesn't work for several reasons.
the most important is that there is no provision for a mechanical fuel pump.

there are systems out there that let you add the belt system and add the compressor on a LA block, but honestly based on cost, I would just find a whole running 5.9 and convert it to carb for your application and add a holley carb pump.

You need the magnum heads and timing cover. Then you are limited to the Edelbrock air gap intake if you want to keep the A/C unless you can find one of the rare Mopar Performance single plane variants.

Rumor has it that the serpentine system from the V8 89-90 Dakotas and Lil Red Express MAY fit the LA small block. These engines are hard to find and someone needs to do a side by side comparison and parts mock up. The timing cover from those engines are supposed to have the fuel pump mount, at least from the pics I have seen. I've also been told the heads do not have the additional holes like the magnums for the bracket mounting.

Good luck with that.

A Dakota didn't get a v8 option until 91 (LA 318), and the serpentine belt on a Dakota didn't start until 93, and those serpentine belt motors were all Magnum motors. Even the 3.9 V6 was a magnum motor from 93 model year on.

The Dakotas were all EFI after 89, so no fuel pump hole in the timing cover from at least 90 LA motor versions on, be it a V6 or a v8 version.

1989 Dodge Dakota Shelby... V8
1991 Dakota Lil Red express , LA V8 with serpentine belt system..... https://barnfinds.com/who-knew-1991-dodge-lil-red-express-dakota/

Might be fuel injected, but still had the LA timing cover, maybe hole wasn't drilled in?? Used a block off plate??

91 dodge dakota Rockauto catalog for timing cover... https://www.rockauto.com/en/moreinfo.php?pk=871879&cc=1087477&pt=5737&jsn=881

The Shelby Dakota was a product of Shelby. At that time frame, they were the leading test ground for Dodge. The very 1st Shelby Dodge turbo FWD cars came out of Shelby. If you wanted a V8 in a Dakota before the late 90 option, you bought a Shelby Dakota. Never saw a Dakota Lit Red Express in real life, have no idea what was on them. That said, a special option truck parts may be pretty hard to come by, and finding someone that knows what changed is going to be even harder.

As far as the LA timing cover, when Mopar went full fuel injection, they had a lot of the old timing covers on the shelf. In typical Mopar fashion, they used up what was on the shelf. The early 1989 production motors had covers for the fuel pump opening. The next round of casting simply did not punch the hole, or drill and tap the bolt holes. The newer Magnum timing cover casting eliminated the fuel pump mounting. I have no doubt there are still some of the original timing casting out there, still a lot of small block Mopars running mechanical fuel pumps, and there are still a lot of guys that still have 1940s and 1950s NOS stuff sitting on shelves.That said, the fuel pump mounting point on the LA small block timing cover was mostly gone from 1990 on, and the Magnum motors never had the provision.

You might find the needle in the hay stack for those rare option trucks, if so, more power to you. Good luck finding them.