Is 20W-50 too heavy for my 340?

I have some 20W-50 VR1 “High Zinc” in my shop and am planning an oil change. Is this too heavy?

Information:

Flat tappet 340
High compression 12:1?
Older engine oil pressure was on the lower side if I recall correctly maybe 30 psi but don’t recall what oil was used.
Lives in Phoenix and it’s getting HOT!

If not what do you recommend?

Thank you!