What is max total timing for a 235? 30 degrees? more?

I have got one of these knock off MSD small cap HEI's. I am experimenting with the springs and limit bushings but would like point of reference. I generally time these by gauge and ear but would like to know really where I am at.

Thanks


1953 Chevrolet Handyman Wagon 36k
1938 Buick 38k
1947 Hudson Commodore 18k