If my memory serves, the "Lovely Jubblies" of my '60s childhood were somewhere between 100-200ml each (of course, back then that was probably 4-8 fl. oz.) -- but given the never-ending controversy over Wagon Wheels, with consumers claiming that they used to be huge back then but Nabisco insisting that they haven't shrunk, they only seem to have done so because people have grown bigger relative to them, it's probably impossible to say for certain unless somebody has kept an original '60s packet.
Certainly I thought they'd only survived as one of Del-Boy's catch phrases. 😉