First, the triangle is not for setting ignition timing. It is used for checking valve timing.
There should be a UIC stamped near the BB. The line between the U and the C is TDC, or Upper Center.
See picture. With today's fuels 235's like about 5 degrees more advance than the BB.
I would set your dial on 10 degrees to start with and set the timing so the pointer is on the UC line and see how it runs.
You can also set timing with a vacuum gauge.
