2020 small block race?

I also went through some timeslips posted on the 2018 race and out of 4 cars and 5 slips the conversion chart listed above was more or less .2 faster on 3 of the 4 cars in the 1/4 mile. 1 was dead on.
So use it as is with the 1.56 conversion factor or use the 1.5835 conversion factor that goes with the majority of the cars?