The internals of Chrome and Safari have diverged dramatically since the fork (which was 7 years ago).

Chrome has done multiple huge projects that changed how things work at a fundamental level like Oilpan (using a C++ garbage collector), LayoutNG (a full rewrite of the layout part of the engine from the ground up), Slimming Paint (a full rewrite of the compositing and painting system), and Site Isolation.

Blink and WebKit are pretty different engines with very different behavior, bugs, and performance characteristics.

WebKit, the enginge for Safari, is not. Epiphany uses the same engine and is available for Linux. I'm sure there's a Windows WebKit browser as well.