Originally Posted by JW51
I'm sure a synthetic oil of appropriate grade would do no harm in a stovebolt, but I struggle to imagine it providing any advantage....

Would a synthetic be less prone to gunking up the rocker shaft?
A synthetic oil would be no less prone to gunking up anything when compared to a modern multi-grade oil.

I have been using Rotella 15-40 for at least 10 years. 10W-30 would be similar in regarding "gunking".