Ihave a 1972 dodge dart custom with a 225 slant six. I would really like
to give it quite a bit more power with a hyperpack manifold but i have a few questions.
Is the power increase significant?
I don't care about gas milage But is it good for just around town?
Is there anything i have to buy besides new headders a hyper pack manifold and a four barrel carb?

I would really appreciate it if anyone could answer at leat one of these questions.

Hello and welcome.

You asking someone to make a recipe for your motor. This is impossible. The issues you want answeres fro are VERY complex. I would reommend you use the search function on this board to learn about the pros and cons of different intakes, exhausts, camshafts, carbs, ignition systems, etc...

There is no "one size fits all" slant six buildup. I can tell you right now that you probably won't be happy with a hyper-pak on a street car, unless you have the expertise and fabrication skills to overcome some carb heat issues and fuel dispersion issues.

Not trying to be rude or get on your case, but you should start by researching.

Sorry to start with some bad news, but hyperpak are getting pretty rare, and very very expensive. If you have the money for it a hurricane manifold would not only be more cost effective, but most likely better performance. The idea of plenum intakes is makes perfect sense to me as most engine stuff is controlling flow and pressure of air into your chamber to maximize potential at a certain rpm. However, the hyperpak was designed for the 170, and without some other modifications mostly camshaft (this was part of the hyperpak combination in the day source: allpar.com) this will be a lot of money for little gain making your hate your slant six and trading it in for the more common 360 .
Headers, are most likely a neccesity (don't quote me on that), but so would a heated course to your manifold to help with warm-up and streetablilty. Once again the only common headers are Clifford which you need to use the Search function or jump onto the "Other" section and read about them. Don't trust opinions outward, but with advisement.
I think money could be spent in other places with better results. In short, Erson group buy camshaft, ENGRBLDR's oversized valves, offy intakes, or super six would be less money and give you a more satisfying result. Yes the hyperpak is cool and I want one too, but to me and others it's simply not the performance item or coolness I want to pay for.
Wes

You'll find lots of good info about using the clifford aftermarket intake, but you'll have to do lots of modification to get it all started, you'll be investing in quite a few things to get it to work reliably for 'street' use.
This intake is OK down low, but it shines best at the 3500 rpm range...with a set of street gears at 65 mph you don't see over 2800 rpm with an automatic... you're best to work up a much more mild street build until you're able to buy the 'easter egg' parts to put together a "hotter" build. It also helps to have a 'second car' until you get the combination worked out (I drove my '74 more times regularly until I could get my hyperpak duster worked out...)

-D.Idiot

Welcome on the board.

Just bolting on a Hyper-Pak intake (assuming you were to find and be able to afford one) would give very disappointing results. Instead of deciding you want to put such-and-such a particular part (or parts) on your car and then trying to predict if that will help or hurt the car's performance, driveability, and economy, it's usually best to start from the other end of the question and define your goals for what you want the car to do that it doesn't presently do, or what you want it not to do that it presently does. Be specific, "more power" isn't particular enough. The more specific you can get, the better will be the advice you get in return. Instead of picking out parts that look and sound cool, start by defining — very specifically — your goals for the car. What do you want it to do, exactly? How will you be driving this car? Where? When? How often? On what kind of gasoline? What amount of performance improvement will be satisfactory: how fast do you need to get to 60 mph? What's your cruising speed on the highway? You say you don't care about gas mileage. Are you sure that's still going to be the case when gas goes back to $4+ a gallon? What kind of budget do you need to stick to, and is it a budget just for the engine, or do you also want the car to steer and stop better, etc.? How much experience do you have repairing, refurbishing, and modifying old cars in general? Slant-6s in particular? Once you've spent some time thinking and planning on those goals and answering these questions, we can guide you specifically to parts and techniques to go for (and those to avoid).

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i know this is a slant six forum but if i where to but a v8 in my dart would
i have to change the location of the engin mounts or lengthen the drive shaft?

Not necessarily, but there are LOTS of other things you would have to change that make that swap not a simple motor/tranny swap.