390 casting #'s someone told me this one's special. confirm?

[jreb333]

i have a 390 in a 1969 F-250 "camper special". the story on the truck/motor goes like this.
1st owner had it til he died in 1995. the second owner bought it from his estate with 96K miles on it. this guy didn't think it had enough power to tow his backhoe so he called up dearborn and asked if they still had any 390 engines in the warehouse. one was found and shipped to him and he replaced the original 390 with the new one. still didnt have enough power for him so he sold it to mein 1996 with 98K mileage. (dumba$$ shoulda just put a 4bbl carb on top and it would have pulled his tractor just fine).

about a month after i bought it i was crawling around in it with a buddy of mine who is considered by many to be a Ford guru and i heard a "HOLY $HI+" come from under the hood. when i went to see what he had found he pointed out the numbers "401" cast in reverse on the front of the engine block. he said that this was called a "mirror block" because those numbers could be correctly read in a mirror. he said it was one of the strongest V-8 blocks built by any company anywhere. a few years later i heard somewhere else that these blocks were built for use in australia.

has anyone heard of anything remotely confirming or refuting these claims?

i would really appriciate some input on this.

(my intake manifold has the firing order cast on the back left side. ive also heard this is in someway special or rare. confirm/deny? thanks)

[FORDification]

I've never heard of a "401" mirror casting. Are you sure it isn't "501", which would actually be a "105" in reverse? The 105 blocks have some extra cranksaddle webbing...but that's really about it. Some have said that they also have thicker cylinder walls to allow for larger overbores, but many Ford gurus say that isn't true. I'e also heard that these blocks have a slightly higher nickel content...but I can't verify that right now. The 105 was simply the symbol the Michigan Casting Center (MCC) used whenever it cast an FE or FT block, as opposed to the Dearborn (DIF) foundry's "352" casting in the same spot, and was put on the 360 blocks as well as the 390 blocks. They're not rare, but a good find....they're strong blocks and a good candidate for a hi-performance rebuild.

If you aren't referring to the "105" blocks, then you can disregard everything I just said.