Which performance parts are right for my 440 Challenger?

I am considering to beef up my 71' 440". Just had it dynoed, 275hp at 4300 rpm, 515Nm tourqe at 3500 rpm. I must apoligize for my lack of knowing how to translate Nm to footpounds, but this is the standard in Denmark. Of course i am disappointed with these results, had blindly beleived the guy who sold me the car, his est. was 400hp My knowledge on engines is little, but i would like to hear from you guys with simular engines, or at least the know how to guide me home.
I look forward to be able to outperform my friends Hayabusa at all speeds.
Help me with your wise guidance please.

Regards Peter  

275 at the rear wheels is in fact close to 375 at the crank, so don't be to disappointed. Remember this is a stock engine and 375HP was the factory rating on this motor. Plus it is actually putting out over 500 ft. lbs. Stock was 480.
You want more, no problem, headers, 750 double pumper, performer or torqer intake.
MSD6al, 284/484 mopar cam. All this will bump you up close to 475 at the crank.
Want even more performance? Install a set of 3.91 gears, and a 3500 stall converter.
With a set of sticky tires you will have a high 12 second ride.
Good Luck
Doc  

Thank you Doc, headers are installed as well as weiand intake and MSD ignition coil and wires.
How about edelbrock victor INDY cylinder heads, a mate recommended this? What will come out of this?
What's a 3500 stall converter? And where to put this 3.91 gear?

Regard Peter  

So do the Converter, it goes in the transmission, gears in the rear end. Aluminum heads? This is more of a drag race only set up and these heads respond best when used with lots of compression.
Once these items are done I would install the cam I recommended and the 750 DP holley. You will see big seat of the pants gains I promise.
Doc  

Ok, now I see..
I'll try this, and respond to you later. May take a while, with my lack of skills and all How much would resonable to pay for these parts in the USA? So its possible for me to check if the Danish importer is making too much money??  
Peter  

You can order the cam direct from Mopar performance, it is about $250.00 US with lifters.
I would order a Dynamic 9 1/2 inch converter, tell them what you have in the car as far as performance items including the gears and tell them you want it to stall around 3500 RPM.
I paid close to $900.00 from the US. I can tell you this is the baddest[best!!] converter I have ever bought and I am 100% pleased with it.
Gears, Search out any of the gear vendors or axle companies such as Moser.
You can order a complete new third member 8 3/4 with the gears of your choice.
Order this with the 1 7/8" pinion, this is the strongest and make sure you get a clutch type posi. don't settle for anything less, the cone type posi is useless behind a 440. You may have to search for a used clutch type posi on e-bay, if you find one the clutch kit is still available from Mopar Performance and it is straight forward to install. Be sure to order the bolts that hold the posi together, they are left thread and should be replaced everytime the posi is overhauled.
Good Luck
Doc  

Thank you very much sir. Good description. I'll let you know how it goes if you'd like.

Peter  

Sounds good, if you want e-mail me direct at 67mopar@sympatico.ca
Doc  

Sounds good, if you want e-mail me direct at 67mopar@sympatico.ca
Doc  

Actually if you know anybody else with a '72-'74 mopars, see if they still have the factory carb, on big blocks it was a Carter 850cfm Thermoquad, and on small blocks it was an 800, they are fantastic and would be cheaper than a Holley. And if you can't find a clutch type Posi you could also get a Detroit locker. It does essentially the same thing but you never have to replace clutches.  
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1974 Plymouth Satellite Sebring Sundance, 440cid, 727A.

850 thermoquad compared to a holley 750 DP? Sorry no comparison, the only thing the thermoquad was ever good for was fuel economy period.
Doc  

Are you kidding? Holley's are finnicky and terrible. Carter's are more reliable and get more power. I will never run a holley. My dad had a 750DP on his 383 charger and it was just garbage so the TQ 850 went back on. More power, better economy, and way easier to live with.  
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1974 Plymouth Satellite Sebring Sundance, 440cid, 727A.

but what ive heard is holley's depend on the person. i do know guys who swear by em but my family has had nothing but bad luck with em and the carters have been great  
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1974 Plymouth Satellite Sebring Sundance, 440cid, 727A.