Engine Rebuild

[420nitro]

To get that strong sound out of your exhust does not require headers. If you desire that "tinsey sound" from the engine conpartment, then yes get full length headers. That in itself will make the overall car sound meaner.
If you want more power over all, then the headers make sense.
I don't believe you need headers to just beat some high school punk's Honda Civic.

I understand that an unmodified classic (at least by a visual inspection) is worth more money so I would personnaly do without the headers and get a set of Flowmaster mufflers instead.
You can also do some internal modifications that nobody needs to know about, to get more power.