The Drifters up till the early 1990's had a hole in the top of the boom tube directly under the rear upright, the electrical wires from the engine ran inside the boom tube and exited behind the instrument panel. The hole in the top of the boom is the week point. In the 503 Drifter you can see the boom through the inspection holes under the pan. In the 582 they don't have the inspection holes, the underpan support for the upright brace tube are in the way.
I believe 25-413 is a converted 503
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