@4vandproud I looked up specifications on the Edelbrock Victor Jr. aluminum heads and they call for a 14mm gasket seat plug with a 3/4” reach. From what I gather on Autolite’s heat range, the 3923 has a heat rating of 3, and the 3924 has a heat range of 4 so it’s hotter. I’m just naturally aspirated EFI and the 3924 is a mostly “stock” style plug from what I’m reading.
I might put a call into Edelbrock for their input as it’s their heads on the car.