Question: I have a three-wheat batter bread recipe that calls for baking in four 16 oz cans. What size pan can I substitute?

Answer: 
Three small (but not mini) metal loaf pans (5"L x 3"W x 3"D) will do it. Check out vintage bakeware in thrift stores to find that odd size, or choose pans closest to that size.
Honestly, use whatever size pans you have available to you and just monitor the baking process. Get creative.