Not sure about the difference in the Motorcraft and Autolite parts. Will guess though that they are close to being the same product. The "R" I think means having a radio interference reducing capability. I am running NGK UR4 plugs at the present time in my 351C4V but have a set of Autolite 25's on the shelf also.
haven't been used for years. Did you find some old stock? Ford owned Autolite years ago and were forced to sell [some kind of law for owning to much of a market] So was it 72' or 73' Motorcraft came about? Bendix bought up Autolite and agreed to supply electrical parts to Ford under the Motorcraft name. What about GM with AC? How come they didn't have to sell off? Hey Bob, can you help out on this auto history? since you've been around forever! Was that you that planted those redwoods in Cali? haha
The '72 model year started using Motorcraft stuff. Autolite was up through '71. I learned this after I had put the Autolight replacement parts decal on the air cleaner of my '72 Torino. DOH!!! Oh well, most people won't know the difference.