I work at Autozone Part-time. Most of the other employees won't even try to find a comparable part if you say anything about a Boat. I am usually successful in finding most comparables, but I always give the disclaimer, on what should be marine. Some times I have to break out the Books in the store, to find comparables, most of the other employees don't know they exist. If its not in the computer, they think it doesn't exist.
I went to the Autozone website and put in the Numbers listed by Tom and they cross-referenced to:
AC-DELCO 84T
AUTOLITE_RESISTOR 124 $1.49
DENSO 5014
MOTORCRAFT 414
I believe my store (Serverna Park Md) stocks these, and we are a low volume store. So most Autozones will stock them or be able to get them in 1-2 days. Just give them your existing spark plug number (or Toms listed number) and they can cross reference it.
Rob
The Eagles Nest
http://www.geocities.com/just_two_more/31CHRIS.html