I am planning on going to H4 halogen Hella headlights 100/80 watt and 55watt low beam, I have done the relay upgrade which made a big difference with stock sealed beams, but I work till midnight every night and live in an area where I see 5-10 deer every night and would like some good lights so I am wondering if my stock 55 amp alternator will handle these lights and if not what should I go to and do I need to change any other wiring if I do go to a bigger alternator? I have read all of Mad electrics info but didn't see an answer to these questions.

a bigger amp alternator is an easy swap. just put a big cable (the same size as the cable going from the battery to the starter) from the terminal on the back straight to the battery, and you are good to go. this is how GM did it starting in the 80's. i've done this to several of my cars, and it does make a HUGE difference in how the charging system works. the lights are brighter, the car runs better, and the battery is always fully charged. it's a win/win/win situation.

Do the math... P = E * I and E = I * R.

But first what H4 bulbs are you planning on running? Your numbers do not entirely make sense. The H4 bulb will be a high/low and normally runs 55/60 watt. These are technically not legal in the US, but if you keep it responsible it is unlikely you will ever have a problem. But in the spirit of keeping it responsible, I would not recommend increasing the low beam wattage. I have seen some H4 bulbs that split the wattage with something like 55/100 watt but I am not sure if those are still available or not.

Likewise the high beams will normally run an H1 bulb and start with 55 watt. These are available in higher wattages too.

I run 55/60 watt H4 and 55 watt H1 Hella conversions on my '68 El Camino. And it really does put out a bunch of light on high. You really might not need to bump up the wattages at all. You can see some details here of before/after (note that both used the same relay wiring): http://home.surewest.net/jahr/ElCamino/Electrical/Electrical.html

When you figure out just what you are going to run, add up all the high beam wattages. So for mine I have 60 + 60 + 55 + 55 = 230 watts. Then divide this by system voltage (might be some debate on *exact* number to use here) or 230 / 12 = 19.17 amps. This number is important to size your wires, select a self-resetting circuit breaker, make sure your relays are up to the job, and finally what your alternator will need to provide. Whenever in doubt, just round for margin as I did when using 12 volts in the division above (using the more typical 14 volt system voltage would have given a lower current). It is always better to have some extra capacity built into the system.

It is also a good idea to state the year you are working with rather then making folks go digging and guessing you are talking about the '67 El Camino? So you are dealing with a 4 light system and small reflector/lenses rather than a 2 light large reflector/lense system. Note that the smaller reflector/lense is more limited with respect to wattage because of the extra heat generated. Too much heat is not good for glass lenses. It makes them crack or worse.