Its squeals horribly in low gear, and alternator is only charging around 10-12 volts, and sometimes stalls when it charges too low, is it the belts causing this problem? or the alternator? or the tension on the belts?

Check charging fuse, replace alternator

the voltage should remain at 14.5 volts at all engine speeds above idle 13.9 volts at idle indicates that the alternator is charging but not at set voltage
head lights are the biggest drain that affects charge rate rate and it it maintains and from you description that is not a problem
when you select a gear it indicates a heavy drain which is a high resistance or a dead short in that circuit that is taking out more power than the alternator is charging
There there is nothing in the gear selection that draws such power
the other thing is that when selection a gear the engine rpm is tool low and the alternator stops charging
for auto vehicles , the idle rpm should be at 800-900 rpm dropping to 750-800 in drive

if the belt squeals why not fix that first? ?>?????
that is correct, if a shared belt resource, is seized it will cause any belt to slip and the alternator to stall , after all they are SHARED.
some alternators do have the regulator in the ECU. for sure.
why guess, tools are cheap. wana buy a tool.>
did you hand spin all shared pulleys to feel for seizer or use a $5
stethoscope on each for load bearing noise, so simple to do...
they sell this tool called a Laser RPM tool, point and shoot.
its cheap,
The correct RPM of the ALT is publised in the FSM and you can measure it.
i take my crank pulley diameter and divide it by the alt pulley diameter.
eg: one is 8" other is 3"
so the ratio is 2.66 :1
so at engine RPM of 800 x 2.66 you have 2128 rpm on the alt.
basic mech, 101.
so if the tool shows way less than that, then bingo, the pulley is slipping, BTW2 not all slips squeal. so.... the tools rule the world of mechanics.
here is the cheap tool i use to find things with wrong RPM.
i put a dab of liquid paper (walfart) on any pulley and this tool
picks it up and bam RPM exactly.
no hands getting caught in belts etc, no danger.

so recap
belt new.
all things on the belt, feel good spun
all things on that belt , sound good $5 stethoscope.
tension on belt , at spec.
if still bad out comes Mr
DT22334A
http://www.amazon.com/DT2234A-Tachometer-chemical-automobile-airplane/dp/B00BKUNOAW

in the real world , sometimes THINGs only SEIZE on the fly.
picture in mind a dry bearing that keeps dragging more as it spins faster. bingo. its bad. and gets worse at higher RPM and soon it
will seize 100% and throw that belt or shred it.

I cant pin down where it squeels
why not drop the belt (cold engine if shared with water pump)
and now it dont squeal.
easy huh, no belt , no squeal.
i truly hope this helps.
there is no reason to guess, besides a new unglazed belt.
ever.

You don't say if the battery is then flat? If the battery is flat, then the alternator is not supplying enough charge and the lights are using the battery power and starving the ignition and fuel pump of power. Connect a volt meter across the battery, engine off should get a reading of about 12.8 volts, start the engine, at 1500 rpm reading of 13.5 to 14.00 volts approx., switch lights and heater blower on, reading should drop then build up again to around 13.2 volts. If this does not happen and it carries on dropping the alternator is at fault. Could be that the alternator drive belt is to slack, adjust belt and test again. If there is a high pitched squeal, that is a sign the belt is slack.

If you have no wiring diagrams,then
you need a repair shop that can diagnose the issue

Check the idle rpm (efi around 900 rpm ) carby around 750-800rpm. Very few alternators charge under 750 rpm as it requires 14 volts to charge the battery and at low revs the alternator will be producing around 11.5-12 volts. Check tension and condition of drive belt.

I would say that you have two problems, 1st is most likely a loose belt for your power steering, and 2nd your light problem could be an alternator, not putting out enough charge, should be putting out around 13.6 volts at all times, I'd give these a try Dave.

You need to have the alternator checked. The tachometer runs off signal from the distributor, but can be indirectly affected by the charging system. It may be as simple as tightening the alternator belt, but I would guess that the alternator itself is going bad. Alternators that are marginal in charging ability anyway (old) may just go bad under the load of charging a fully dead battery.

The squeal is coming from the alternator belt, When the temp is low, the belt is hard and glazed and lost its ability to create friction.

If the belt is 3 yrs old or older, change it. If it has oil or anti-freeze or grease on it, change it. If new, add more tension to the belt.