That should work well in your car. The 85W-140 has been used and recommended here by plenty of folks for the transmission and differential.

Hi here as well  🙂

I am assuming you have a manual transmission.

If so, an 80W-90 would be a better choice as I think Chev was recommending SAE 90 in the summer and 80W in the winter at that time.

Some will say not to use GL-5 in old transmissions with brass/bronze bushings in them.

That was true many many decades ago, but modern GL-5 oils are buffered so they are safe to use.

When Gene Schneider was posting here, he always said he agreed with this and used GL-5s in his own cars.

Thanks for your input. Yes, a manual transmission.

I have been using the GL-5 85W-140 in my 37 for several years now but who can be sure what's going on in the transmission. One just hopes you are preserving old vehicles and not doing them any long-term harm. I have not owned this 50 very long and wanted to change the fluids for winter as who knows what previous owners have used. I didn't want to assume that I should just use the same for both vehicles.