[Byots]

David - Does your 79 lb number include the caps and the covers on the sides of the lifter galley? I seem to remember the Shelby aluminum block is about 130 lbs with caps, because the original Ford aluminum 390/427 blocks are 110-113 lbs with caps and I recall the Shelby block has about 20 lbs more beef. The original aluminum blocks were cast for the most part from regular cast iron block patterns, except the 427 version had much thicker cylinder walls, and I really can't think of areas where material could be removed and still feel comfortable with it at 600hp levels for extended periods.

Edit: I just looked through your pictures posted on the Kirkham website and it looks like the major areas of weight savings are the sculpted front and rear faces and removal of the external water jacket surfaces, so it makes sense now.