If it is an old engine that has been sitting you would generally want to select an oil of proper specification and use a natural oil. While there is absolutely nothing wrong with a full or semi synthetic my experience has shown they tend to leak a bit more around seals. Maybe it is a thinner base or higher level of detergents but if you have a loose seal or gasket that synthetic will find it's way out faster. No analytical study just experience in the field seeing what happens when guys switch.
If you can speak with the man who owned it find out what worked for him and what the build may require.
Read about ZZDP and find out if your engines needs are met with your selection.
If you are unsure what exactly you have engine wise grab a jug of 15W-40 Rotella, Lucas Oil Stabilizer and a ZZPD break-in additive such as CompCam159 or Lucas Break in additive. Use as the instructions advise, you won't hurt a cam and lifters that way. It is all at the local parts store.
https://www.summitracing.com/parts/cca-159
PM if your in need of more specific info
I reviewed your dyno sheet and you have a 350 bored .030 for 355cid with a hydraulic cam but it doesn't specify roller of flat tappet.
YOU BETTER USE ZZDP unless you know first hand it is a roller engine.