300SDL IP timing

[werminghausen]

I take care of a nice 87 300SDL with 300Kmiles.
Is there a good method to set IP timing without using the Bosch tool.
Motor is sound, good compression 32 bar still, new injectors 140 bar. I repalced the timing chain lest week and now I want to set the IP timing.
I guess that start of delivery should be around 24 to 26 degrees BTDC but I am not quite sure. Is there anyon who knows the data and the best method I can do in my own garage. Thanks