Spark Plugs in ’68 Mustang

On the front of the head there will be three cast ribs or bumbs kind of like a bar code if they are gt-40 heads it will be between the freeze plug and a mounting boss for accessories but closer to the boss.

Jim,
The casting ID number you need is unfortunately on the underside of the head. My guess is that you just have a later model, 1975+ head where Ford went to the smaller plug design. If you're so inclined or interested, which I'd be, pull one head, flip it over you'll find what you're searching for and then look at the link attached to see what you've got.

http://www.mustangii.net/head.asp

I tend to agree with the majority on this one. Go ahead and use the automotive plugs, just be certain to change them in a timely fashion. AS Tim said bad things happen when you dont stay on top of the little things.

jim i use autolite 24s the 88 cent ones. and use it in salt water, the same water you use yours im sure. i bought my conversion kit at www.vintageperformance.com it was 100.00 for the conversion kit and a high perf coil. you can order one for that mustang while your at it.

Those stainless steel plugs are about $4.85 a each. A regular plug is 84 cents each. You take the points and condensor out and replace it with electronic unit. Take screws out and screw in new part, very easy,(use a screwdriver with magnectic tip)and use the same rotor button and cap. My mustang has a flat top Mallory distrubutor.(had single points). It starts easier and made a big difference on throttle response, and I gap my plugs wider now. It was worth the $90, no more sanding points or replacing points, and moisture doesn't affect it.

I use autolite 26 in my 1966 mustang. They will rust around the ceramic part. But I change them every year (cheap). About 9 years ago I left the plugs in for about 4 years and the number 5 cylinder shot the ceramic part out of the metal part when I hit full throttle. The plug and plug wire hit the motor box, man what a noise, we thought someone shot a gun at us. Luckily the wire didn't get in the pulleys and belts. Last year I indexed all my plugs toward the intake valves, but I noticed they don't stay as tight because of the spacer washers. I took the points out about 5 years ago (the best $90 ever spent) and I use an Accel coil which is designed for heat and vibration, it has a gel instead of oil.