Sounds like you found a good trade route already 
Keep doing what you're doing; sounds pretty good to me.
Ny gatelane parts to tau 23 gate works and cardemine from cali back to Ny
engine parts to dublin and gold back to rheinland ??
highest proffit on discovery considering money/time is malta <> ny
trade cardamine from malta to nb, and refugees (or something simmilar if forgot commodity) to malta
go through alaska, omicron 90(or similar), unknowns, malta
thats shortest path
train is so strong that npcs cant damage it, but you might encounter problem with player battleships camping docks
mine copper and silver in colorado. copper can be sold on planet colorado and i think the ageria base there.
Niobium from Tau 23 to Manhattan in New York is a profitable route.
Another run that may be dangerous (but profitable) is running gold from Dublin. If you're brave enough, you can mine it near the Leeds and New London jump holes, but expect Corsair encounters. To play it safe, you can buy it from Battleship Hood or Gates, or maybe you can strike a deal with the Mollys and buy it at bargain prices. You can trade the gold at Manhattan and bring back pharmaceuticals and food rations.
Cardamine to Manhattan and Light Arms from Detroit in reverse, via Alaska and Delta is another good, profitable route
The only time I ran cardamine was during the storyline, when I accidentally ran into the Flint in the Badlands. I avoided the trade lanes and went directly to Manhattan, leaning on the advice of Paul Steed, the Junker at the Manhattan bar. Let's just say the last 20K was frightening until I got to the docking ring. Liberty Police Inc. don't play around.
:o
I managed to make quite an amount of money by shipping Ground Vehicles (or was it combat vehicles, whatever) from Planet Marne to Planet Quillan. It's a awfully short run, and if you've got a big ship and are on good (or at least neutral) terms with the Gallic police and navy, then its the best run I can think of. Lots of money in only a short run. A smart thing to do is to bring something back with you while you're at it: they had something on Quillan that Reims Station wanted, don't remember what it was though... but I think it was Hydrocarbons.
If you're wondering on how to get on good terms with the Gallic faction the answer is simple: kill Outcasts, makes almost everybody except their allies happier. Either them or Xenos, don't know about them though.
It's a good way to make money, I was able to save up for a Manta with that run a few times using a Crusader. 
I just started playing Discovery 4.85 and it is AWESOME! Now I'm torn! I love Frontierspace 1.75, but Discovery 4.85 can actually give Frontierspace a run for its credits. What's a Freelancer to do? :shock: