Back when I had my 66 ply I swapped out the 4 wheel drums for wilwood discs and the sure grip for a spool and IIRC dropped .3 off my 1/4 et. I was amazed till one of the old timers told me that I had dropped a ton of rotational weight and what he said was every 10#'s of rotational weight was equal to 100#'s of static weight.