It is a "de-bored" block with the reduced bore size of 4.050"
This was done to fit into certain "class" racing 6.5 litre engine sizes.
It is the extremely rare lightened "race block" that eliminated the heavy cross bolt mains, extra overly heavy side oiler
oil passages, and the very heavy screw in freeze plugs.
This block took 15 lbs. off the front end making handling much better.
Also, to throw off the competition, nowhere on this block does it say, "427"
Many racers just assume it is a standard 390 block,
little do they know...
I also have the matching rare, lightweight cast iron crankshaft.
The cast iron "racing" crank is 17 lbs lighter than the heavy forged steel standard 427 crank.
I can make a package deal, but it won't be cheap
Gee, this sounds like every e-bay ad I read