i have a 75 dart hang ten with a 225 in it. it runs okay at idle but as soon as i put it into gear (it is an auto trans)the motor starts shaking.when i put it back into park it goes back to normal.what can this be?  

Many things can cause this problem, first check the obvious, are the motor mount and trans. mount in good condition. If so check the carb fuel mixture screw and vac. lines to make sure they are attached to the carb and the distributer.
If the problem continues I would recommend checking the engines compression. A low cyl. pressure on any cyl.  will cause the vehicle to shake when put into gear.
If the cyl. pressure is good then likely it is a tuneup related problem, possibly plugs, wires, cap, timing out of adjustment, vac. advance may not be working, all these things should be checked.  

ok, thanks