1984 B250 odd issues and a few questions

Hello,

The van is a $600 band haller but, I happen to like to drive it.
Anyway, onto question #1, if you give it too much throttle and it tries to downshift, it will jerk and sputter and you will almost always sit on the side of the road for a few minutes until it will start again. We drive it VERY easy, to say the least. You cannot let it or make it drop down into "passing gear" or you'll be sorry. IDEAS?

The carb has been rebuilt, the plugs, wires, cap, rotor, fuel pump and filter, the coil, the battery, the battery terminals, the airpump belt and air filter are new. The trigger pickup is within resistance spec, and the "brain box" checks out as well.

The motor is a 318 V8 all stock with 187k on it. it starts great on warm days, a bit tough to get going in the cold since the choke thermostat went bad and someone wired it open.

also, does anyone know the stock part number for the alternator and what its output is? also, is there a high-amp alternator that will bolt in?
There are alot of gadgets on this thing including a full stereo and H4 headlights, so we'd feel better with some extra juice.

Thanks,

Jay