If you align the special links with the marks on the cams, then turn the engine over, the marks will not align every time cylinder #1 is at TDC. You need to keep turning the engine until the bottom link is on the mark on the crank sprocket, which you can't see unless you remove the front cover.
Here's what to do when changing cams if you to be 100% sure you have the cam timing correct:
1. Turn the engine over by hand until the special links are aligned to the marks on the cams. This takes anywhere from 1 to 100 engine revolutions. After a while you can see a pattern of the links moving, which I think was every 6 or 8 engine revolutions. Take out the spark plugs to make it easier. Put the engine to TDC using a rod on cylinder #1, and check that the marks on the cam sprockets all line up. Take a photo with a digital camera for reference.
2. Remove the steel cover over the tensioner.
3. Put some pressure on the chain guide so that the little cam on the tensioner moves so that the holes line up, then put a pin in the tensioner to lock it. I use a filed down allen as a pin.
4. Lock wire the front of the timing chain making sure that you can still remove the cam sprocket. I use safety wire wrapped around the chain and chain guide.
5. Use something to tension the back of the timing chain and remove the tensioner (I use welding wire). The goal is not to let the chain slip on the crank sprocket.
6. Lock wire the chain so that it cannot slip down, while allowing the chain guide to pivot to give some slack in the chain over the cam sprokets. This is the most critical part. Use multiple pieces of wire.
7. Remove the cam caps and remove the cams. You will need to manipulate one cam at a time a lot, but they will come up.
8. Swap cams or whatever you're going to do. Don't forget to put the correct sensor wheel on the correct cam (they are marked IN or EX).
9. Put the cams back in, install the cam caps, put the chain over the cam sprockets so that the special link matches the marks. Take care not to turn the engine over nor move the chain.
10. Take up tension on the chain with the rear guide and install the tensioner. Remove the pin to release the tensioner.
11. Check that the marks on the cam sprockets line up horizonally. Refer to photo if necessary.
12. Remember to set valve lash (between the valve and rocker, not the roller and cam!).
13. Check everything looks OK, and you're done.
I know the whole process of keeping the chain on the crank sprocket is a pain, but if you do it this way then you can be almost 100% sure you have the correct cam timing.
If the chain does come off the crank sprocket, then all is not lost. Keep going and install the cams so that the horizontal marks line up. Once done give the engine a couple of turns, find TDC using a rod on the piston, and then check the marks on the cam sprockets look good. Use a ruler across them if there is any doubt.