I have a stock 1980 sporty with fresh top end, Bendix carb, and Dyna S ignition with 5 ohm coil. Been running HD 4R5 as the recommended plug based off the stock ignition with a 3 ohm coil. The equal is a Autolite 4123 which I have been running with some success in getting the plug to burn right. The recommended plug for a 79 sporty is the HD 4R but that ignition was points with a 5 ohm coil. The 4R is a little hotter plug but about 1/8" shorter than the 4R5. I assume the 4R will be flush with the head or slighty recessed. Does anyone see any issues running the 4R?