Most galvanisers I have dealt with in the past have a system in place where they will do small jobs, below a certain weight, for a set price. The amount you can get done below the weight varies from company to company. I found one where I managed to get a full set of body callings from an early 110 (with 2piece doors) CSW, the front bumper, a pair of rear bumperettes, an A bar and some other , smaller, bits done for 75 pounds. This was a few years ago though. Typically they will not prepare them for you, so you need to remove any paint, I did it by chucking the bits on a garden fire. Rust is not a problem, the acid pickling dip will take care of that. When you get above the fixed price weight, they price jobs by weight. The item is weighed before being done, then weighed again. You pay for the additional weight of zinc added to the original weight of the items.