Painless wiring / suburban tail lights

[72SUBGUY]

I recently installed the painless harness in my 72 suburban which must be a universal "direct fit" according to their catalog.
The tail / brake / turn harness routes along the frame with the Painless harness and factory is inside the front left front kick panel.

Is it worth pulling the wiring out of the bulkhead and routing them the factory way?

Is it feasible to install the wiring from the bottom up via the frame route.
I would like to just use the frame rail route but I'm not sure how many layers of steel I'll need to drill through to make it to the tail lights from underneath.