I think every car since 1966 has run a negative earth system.
Upgrading the headlight wiring is reasonably straightforward, sounds like you were made a shareholder in that guys new car/motorbike/holiday
Once you understand what needs to be done, it can be achieved fairly simply.
One method is to have a new harness that simply plugs into the old headlamp sockets.
It then operates high current relays to power the appropriate lamps.
The advantage, is that it is truly a plug and play system, plus all the OEM wiring and switches only have to handle ~200mA to operate the high current relays
Get the relays to do all the hard work, that is the key
Oh, and lamp wattage is NOT the last word.
There are inserts now that produce much more VISIBLE light , in the right spectrum, and draw moderate current.
For example: -
http://db.hella.com.au/cgi-bin/catalogu ... flrecid=20
Also, there are legal limits on headlamp wattage, don't get caught blinding the rest of the planet
HID [High Intensity Discharge] systems are not entirely the answer either apparently
Upgrading the alternator is a fairly simple exercise too, but you need to understand a few things about that.
First, the cars original wiring is rated and therefore [hopefully] protected for the standard alternator output, for example 45A.
Upgrading to a unit which is capable of 90A output has the inherent capacity to overload the
existing wiring
UNLESS that wiring is also is suitably upgraded or piggybacked with wiring of sufficient gauge to do the job.
If for example you fit a zillion megawatt sound system to a 1971 Datto, with a 120A alternator, you can simply run new power feeds and auxillary relays to the amp etc and everyone is happy
Try running the system from the existing wiring and you won't have to wait long for the fireworks
Second, if you upgrade the alternator,
because you can, then you
MUST fit some maxi fuses to protect that 30+ year old wiring.
Also, an alternator needs to get above a critical RPM value to start outputting some serious grunt.
If you are wanting lots of power at idle, for whatever reason, that will take a fairly big sucker of an alternator and LOTS of adequate circuit protection.
Think Highway Patrol, stationary car, engine running, radio on, A/C on etc. etc. etc.
As the actress said to the Bishop, you
MUST have adequate protection