Unless things have changed, I am pretty sure that drilling ANY hole in a SFI certified bellhousing renders the SFI sticker invalid, and the bellhousing itself can no longer be recertified. The only exception is if the hole was put there by the original manufacturer, and was SFI certified with the hole already in place. Many have drilled a much smaller 3/8" hole in the backside of the bellhousing , for the ability to adjust static spring pressure , but to put a hole in the path of a rotating flywheel and clutch, especially anything approaching 3/4" , is something that I would absolutely NOT do, UNLESS you have printed documentation on a NHRA letterhead stating that such a modification is acceptable. On both my FE and SB Fords, I have checked clutch air gap thru the clutch fork opening. Certainly not as convenient as a hole in the bottom, but since Lakewood no longer offers a FE scattershield , turning one into scrap metal with a drill bit is certainly not something I would consider doing.
