I'm new to this but my question how can I get 500 to 600 hp out of my 78 dodge d-150 long bed truck. I was told this is one of the worst motors to build can someone help me.I'm also going to drive it sometimes on the road but going to race it most the time.  

500 horsepower is doable, but 600 will take work. In a truck I'd advise building a torque engine rather than goinf for all-out power. The main problem with the 78 440 is the miserably low compression. You'll need to do something to build compression in that engine. I'd start with a piston/block combination that puts the top of the piston right at the deck, then a good, multi-angle vavle job, bowl blend, and port matching for the heads. For a 500 horsepower build, a good Comp hydraulic flat-tappet or better yet a roller will work. If you want to get close to 600 horsepower, a solid flat-tappet or solid roller would be the way to go. Either way, a single plane intake and 850-950 cfm carb will be required.

I'd seriously consider building a nice 400 or so horsepower engine that builds lot's of torque, it'll be more drivable and have plenty of power to get the truck off the line, without killing your budget.  

This is Mike from MRL Performance and this is what I think. 440 hard to build? No Way, man! If you want 600hp, thats not hard to do, but it will cost quite a bit more than 500hp. But drag trucks can be made very light and work quite well in drag racing. Stock heads are out, just because there are much better heads on the market for a reasonable price. 600hp on pump gas is very doable and its not hard.

If you like you can email me and I will help you get this project in the right direction. mrlperformance@peoplepc.com  

Ported & polished heads with 2.14/1.81 valves. Torquer or Permormer Intake, 750 or 800 double pumper holley. 292/509 mopar camshaft, 1 7/8 headman headers will get you to 500 horse with a 10/1 compressio ratio.
You will need a 3500 10" converter to make this camshaft work in your truck.
600 horse, will need the following a solid cam in the 290duration 600+ lift range.
A Victor intake, with a 1050 dominator carberator.
11.5/1 compression.
racing gas, or alcohol.
4200 9 1/2 dynamic torque converter.
2 1/4 inch headers.