350 loader requires at least 800 lbs. in the back if there no rear attachments like a hoe or ripper.
OEM 350 weight set was- four weights and two brackets to hold them. Each weight is 200 lbs. A used parts yard is likely to charge $1 per pound plus another hundred for the two brackets. Original set had three # 8255CU weights and one U20033 weight at the bottom.
350C loader uses the big single T33431
350C loader used one big weight instead of a stack.
There are also sprocket weights.