I will not pay for work before it is done.

The way the economy is shops--and others--have been screwed over by customers who never come back with the money. Then what do they do, try to sell your parts that few people want to buy.

If its a engine block and along with it you drop off new pistons to fit in the bores, then they got something worthwhile to sell, your shorten axles would have few buyers if you pull a no show.