The #4 plug looked pretty good when I pulled it out and looked at it. I'm going to replace them all anyway and I'll take a closer look at it when I do.

I removed the ground strap and cleaned it with water and baking soda as a formality, but it looked really clean. (Cleaner than I expected it to be.)

Put Autolite 605s in and got everything greased up really well and it still had a bit of a misfire... I waited until this morning and checked out the coils which were all fine... after revisiting the wires I discovered that my #5 wire had some carbon inside the boot, looks like it got fried somehow (bad connection to the plug is my guess). Got it replaced and the misfire seems to be gone.

Looks like it was the result of Bosch plugs and dying wires. Had a bit of a scare when I first fired it up as I saw some antifreeze under the #5 plug, but it turns out that I must have bumped the hose and it had started to drip. Put it back into position and tightened the hose clamp and we're good again.

I'll clean her up this afternoon and post some pictures.

Slimsammy:
Thank you for the follow up. It is always great to hear the final fix once the problem is resolved.

Enjoy the smooth operation!