I think if you do some home work you'll see the difference
in good prepped manifolds and headers on a street motor is negligible unless of course you need every single iota of power.
All the extra troubles like burned wires, plug/starter access, rejetting,
blown gaskets, extra heat , not to mention buying a
mini starter and new pipes, yea headers can be a real bargain sometimes.
I'd bet if he had the distributor reworked and the carb jetted
properly, he'd find more power than he had to start with.
I'd say he'd be happier after buying some dyno time at a good tuning shop and a hell of a lot cheaper.
If memory serves, The Flying Green Brick used well prepped
340 manifolds at 450 hp.
Have seen plenty of posts made by people who actualy have experience with extruding manifolds and they tend to say that its realy not worth it.
More power thru the whole range is always worth it,it means that the engine is running more efficiently.
Blown gaskets at the head are a non isue if you use good gaskets and never overtourque you headerbolts (good gaskets=anything that is not them cheap papergaskets)
Use the correct plugwires and they wont burn. if you have an isue with this,you could probably make a simple heatshield,just like the stock HP manifolds use anyway.
Pluggs are a non isue aswell,they are not that hard to get to once you figure out how to do it and what combination of tools work. and realy if you have to change your pluggs often enough to make this a problem you have other problems.
Starterclearance? are you kidding me? once again if you have to change your starter often enough to make that a problem,something else is real wrong somewhere. and no you dont need some special starter i have personaly changed a stock fullsize starter on my duster in the middle of the winter and while i cant say that it wasnt that much fun it was still doable even in -25C on my back in the snow out on a street.
Ministarter? well if you real want one sure get one but its not always required (only instance i know that they are required are on Early A bodies with underchassies headers and those cars are crazy tight) and they are not that expensive anyway,you can find them in junkyards on alot of later trucks. they are lighter and more powerfull.
Most exhaust shops can make most of your stock exhaust fit with a set of headers with ease.
Most engines need a rejet and tune anyway and to be honest headers usualy lean out the mixture in the firstplace wich is just great since most cars run to fat anyway.
the simplest way to make a 500+Hp engine into a 450Hp engine is to add manifolds.
Reality is that the the best bang for the buck and simplest way to more power is a set of headers.
I will agree that headers create more underhood heat.
