check ignition timing, leads, cap and rotor, coil (cracks - common to see) worn injectors/ sticking injectors, map sensor, oxygen sensor, fuel pump could be anything. id start in that order
A Ford Explorer that runs rough may be experiencing a clogged fuel filter, dirty air filter, or worn spark plugs. A proper tune-up can solve most problems associated with an engine running rough.
you probably got a cracked head
Have you checked the o2 sensor, map sensor. will cause rough running problems assuming it hasn't got a blown head gasket. does it start on six cylinders when stone cold? assuming it's a six cylinder.
you could have a bad fuel pump, or you caould also have debris in your gas tank.
jerking speed 40 50
a 1962 Ford Falcon Futura 2 door sedan in a low retail situation could be worth $2500. In poor condition, probably $500 to $1500.
the aux shaft your refering to is the shaft which runs of the the timing chain which in turn drives the distributor.
Check your vacuum hose.
leaking intake gaskets...
Pressure test the convertor.
hard to say but if it runs rough & this is related you may have a leaking intake manifold or head gasket causing vacuum loss (reason for rough idle) & leaking out the antifreeze - both are expensive to repair
Auto Zone will check your engine codes for FREE. Then go from there.