Title goes with Frame or Engine?

[BRENT in 10-uh-C]

I fielded an interesting question on a topic that has been around for years but maybe modern laws change the obvious answer.

Scenario;

An incomplete Model-A chassis is being dismantled by a hobbyist. One buyer buys the engine and transmission, ...and a different buyer purchases the chassis and what is left of the body. Both buyers want the title. Which buyer does the title legally go to?