Stop in for a cup of coffee

90 was the factory for over 10*F, so 75W-90 would probably be the best modern equivalent.
Might see what Dr Diff or some others have to say but the 140 seems really high viscosity in comparison.
As a tribute car it has to do street and strip, and I assume your not tearing down after every event or two. That's one aspect about engine racing oils people seem to ignore when they use them on the street.
Yeah email Cass at dr diff. Cass is THE subject matter expert. No offense to Matt as mat is very knowledgeable as well. But Cass has been dealing with these things on a daily basis and that’s why he’s Dr Diff. Outside of this forum , he’s one of the very few I’d trust in anything Mopar