my vote is exhaust leak, especially if you have gaskets between the head & manifold and or still have the heat riser spring at the right side doughnut.

Don t forget about how much you will actually drive the vehicle , most of us have collector car/ truck insurance with mileage limitations . At best i would drive my car maybe 5000 miles a year , so a 100,000 motor would take 20 years ..

Remember that the 390 was NOT the top of the heap for Ford fans back then, it was just the common passenger car BB.  The 427 had been around in various forms for quite some time and 428 CJ came out in 68.  Since then, the 428 has shown up in a variety of cars, none of which would be scared of a 383 and most wouldn't worry about a 440 either.  CJs still hold NHRA records.  Bottom line, these guys are feeding you some great info and if you go with a 445 built like they are saying then your Mustang will kick the snot out of everything you've talked about including your Challenger.  BTW, your Mustang can be built to run rings around your challenger on a road course as well, the after-market for those cars is staggering!  I know you're gonna have a blast with this project.

If you have the Edelbrocks, a Performer RPM, a 750/780 carb and a set of headers you should be able to give the Runner a good scare.  I used to be able to hunt 383 cars with similar stuff back in the proverbial day.  Just stay away from the 440 cars until you get the stroker and some cam in there - darn Mopes 440s are pretty strong on the street....experience talkin' here...

Quote from: Agar426 on November 16, 2013, 12:07:32 PM

Would swapping a set of Edelbrock heads on the existing engine be beneficial, or are they better suited to a higher end build?  If viable on the stock engine, then the header issue would be solved, albeit with a significant cash outlay for the heads.

The distributor is the stock points distributor....would swapping to an MSD or the like be a good move on the current engine?  If so, which one?  MSD Billet?  MSD ready to run?  (what's the difference between those two anyway?  I know the ready to run doesn't need the box, but otherwise, is the ready to run comparable to the billet with the box?). 

I don't want a race car, but I want it to be strong.  I want to line up to my cousins 383 Roadrunner and be able to know that he will have a hard time keeping up with me.....either on the strip, or on a road trip!

Good questions

1 - Swapping a set of Edelbrocks now, wouldn't be bad, but you'd also have to make sure you had the proper flat tappet springs.  In addition, it would likely drop compression slightly.  However, if you had the budget to do that, yes you could.  Combining the heads, headers, good exhaust and an RPM intake and nice Holley would give you some gains.  Not incredible, but it would make more power.  If the 383 Road Runner is anything more than stock, I would not expect you to beat it without going inside the motor, but my hunch is it would be close depending on his build. 

One very good thing about that plan is you don't have to worry about breaking the top exhaust manifold bolts.

2 - I recommend the MSD, the ready to run is good, but having a box is better because you can get a rev limiter and you get multi spark at low rpm. You can always go back and add a box though  Even with those though, you need to recurve, because they deliver with slow curves.  The curve doesnt really effect peak HP, but it makes a hell of a difference in part throttle response.

3 - Remember, a vehicle is a sum of its systems, this stuff isn't cheap.  There is an old saying, fast, reliable and cheap, (if you don't spend the cash) pick any two.   

Last thing, 383 Mopars aren't the fastest things, but they run well and respond well to aftermarket parts, so don't expect to dethrone him easily.