What's the purpose of the heart and blood? Will you be able to see it? Do you want the puppet to be able to bleed? Will he have an exposed chest cavity?
It's an interesting question. I think if you're looking for something that can be manually pumped, it'd be easier, but something mechanical might be tricky to get pumping in a cycle -- at least, that would be tricky given my technical knowledge.
If manual, I'd say get some plastic tubing for the veins, and maybe a strong balloon or two for the heart, and have a manual pumper (also made of a balloon?) below, that you can manipulate. Pump makes the heart expand, releasing makes it go smaller again.