Athearn?s Ready-To-Roll GP35, based on the Rail Power Products Tooling, represents a phase 1a version that was produced from October, 1963 to February, 1964. This was arguably the most widely-used variant of the GP35. Some of the spotting features of this phase found on the model are:

? Multiple latch on the engine compartment doors.
? Triple-louvered sets on the battery box covers.
? Open-top 36? radiator center fans.
? Flat bottom cab number board housing .
? Flat inertial air filter hatch.
? Thick side sill.
? Low profile fuel tank.

? Scale width hoods.
? Equipped with DCC Quick Plug technology.
? Directional headlights.
? Prototype specific details applied.
? Foot board or snow plow pilots.
? Cast metal air horns.
? Celcon Handrails.
? See-through fans.
? Athearn?s Next Generation Ready-To-Roll mechanism with Hex drive lines.
? Machined RP 25 Profile metal wheels.