66 Formula S engine color

Resurrecting an old thread.

I'm trying to order some single stage urethane paint for my 1965 engine.

There are two different paint codes for International Harvester red:

#50:
http://paintref.com/cgi-bin/colorcodedisplay.cgi?ditzler=70019

and #2150:
http://paintref.com/cgi-bin/paintdetail.cgi?paintx=1966%7CInternational%20Harvester%7CHarvester%20Red%7C10088

50 is much darker than 2150.

Others say to use Chrysler E5 which is 2136 in PPG/Ditzler
http://paintref.com/cgi-bin/paintdetail.cgi?ppg=2136

The Chrysler E5 seems to split the difference between IH50 and IH2150. Anyone have any advice or opinions?