I just bought a '79 Raleigh Sports 3 speed and I noticed that it feels like it's pulling to the left when I want to go in a straight line. Does anyone know what might be causing this? Bent fork? Bent frame? Bent rim? The front rim is definitely out of true but not that badly.

Check the back wheel. Is it pointing straight forward or off to one side?

If the back wheel is pointed straight, check to see if the entire wheel looks off center to the right. If it is, you need to have the alignment on the rear traingle fixed.

or it might need the rim dished

Or the fork may be misaligned, all of these can be corrected.

https://www.sheldonbrown.com/frame-spacing.html

https://bikeforums.net/showthread.php?t=260417

Check these two above links. These will help. They helped me greatly with exactly the same situation you have. The first, from Sheldon Brown, is mainly for frame spreading, but the bending and measuring techniques are applicable for aligning the rear triangle.

The second link is in reference to a bike that I had the same trouble with. Ended up the rear triangle was not in line with the front triangle, and the fork legs were bent to the side. I used the advice from both pages to get the frame in the thread in good shape, and have since fixed a couple more that weren't tracking correctly.

The rear wheel is straight and as far as I can determine the rear triangle is straight too. However, the front forks do look slightly askew and there are more than one loose spokes on the front wheel.
Here's another symptom related to the tracking problem. I performed this little experiment this afternoon. I stood the bike up and while standing beside it I held onto the seat. I had the front wheel pointing straight ahead and the bike was in a perfectly upright and balanced position. When I let go of the handlebars the front wheel immediately turned all the way to the left.
I just got on here a few minutes ago so I haven't had a chance to check out the links FRANKIEJ.

ok, one of the forks is bent too far forward. When I sit on the bike and turn the handle bar hard to the left I can feel the bike get lower beneath me. When I turn the handlebar hard to the right I can feel the bike rise up quite a bit beneath me.

I was unsuccessful in clamping a 2x4 to the fork and getting the clamps to stay on. Other than taking a rubber mallet to it I'm not sure how I'm going to bend that fork backward.

You do not want to be bending anything in or around the fork (unless its steel and VERY minor) - if it's bent get a new one.

Do the string test (see Sheldon Brown) to measure the frame straightness from the headtube back.

If the back end is straight, then first LOOK at the forks to see if they are bent. Typically, forks bend back in a front end crash, so stand on one side of the bike and see if the top 6-10 inches of the fork leg is at the same angle as the head tube. Now look at the bike straight on and see if the fork blades are pushed over to one side or the other.

If the fork is bent, you can bend them back if they are not too bad, but you will likely need special tools.

The fork that I clamped the 2x4 to was a Schwinn flat bladed fork, so in my case it was easy. On a tubular fork, I don't know. Anything to increase the leverage that might slip over one of the legs. I tried to bend my fork without using the 2x4, and it was possible, but much more difficult to control the bend. With a tubular fork, I'd imagine that the extra leverage would be a must have. Any way you go, it's a crap shoot and you risk irreparable frame/fork damage, so go slow. Also in my case the legs were bent to the side, so you may have to come up with your own ideas for forward bends. I've sucessfully bent a steer tube back into place, but never individual fork legs.