correct Spark plug 1953 Chevy truck ???

[Dale49]

What’s the correct spark plug for a 1953 Chevy 3100 1/2ton truck (standard GMC engine 6cyl. 216 cui) ?
AC Delco R43 , Autolite 303 ... copper core with .035 ? These are just examples that I found on the web for that truck. Not sure about the .035 gap (if that’s a useable spark plug).
Anyone who has a clue ? Thanks in advance !

[Deve]

Dale I am not sure of the heat range issues of spark plugs. I never really learned all that. I DO know that .035 is the accepted gap. I have heard that .040 gets a little better performance which allows for another part number from E3. E3.52 is the correct part for our engines and is not re-gappable (at .040). I have done some mileage tests when upgrading to HEI that does show they get better performance, but that is with HEI, not a 6 volt points system. What I am saying is, I do not really know the difference between R43, R44, R45, and back in the day, my 1973 AMC 232 6 cylinder used R45XLS. (I was told that was for radio interference but not sure). I do not think our vendors all know the heat ranges either since all three of those are available through different vendors. One vendor will sell R43 exclusively, while another sells R45, etc. Champion makes the 66 for us too!

Here is the HEI testing on this: http://devestechnet.com/Home/HEIgnition near the bottom of the page.

http://devestechnet.com/Images/Projects/HEIgnition/HEIProject0065lg.jpg