Oil choice for 1962 Lancer? What do you use in your Slant Six?

Hello everyone. I recently picked up a 1962 Lancer (unsure of whether it's a 170 or 225, although it probably doesn't matter for this question). Miles and maintenance history on the motor are unknown. Does seem to run decently.

What's a good oil weight? And, do you personally use an oil higher in ZDDP or an additive? Or do you feel that's unnecessary? I know the ZDDP things has opinions all over the map. I'd be interested in hearing what folks here actually do. Thanks.