[blykins]

Yes, the A460 block.

With a factory block, you can only go to about 550-560 cubic inches safely. The A460 block will go to a 4.600-4.625" bore, which is considerably larger than the capacity of a factory block (usually max around 4.420-4.440").

Otherwise everything costs the same....same crank, same rods, same piston cost, etc.

IMO, the A460 head is simply a better head and that will show up in the potential while porting. The P51 head will top out somewhere around 400-420 cfm, while the A460 head will go 500+.

Header size needs to be 2" to 2-1/4".

IMO, the BBF is *the* pinnacle of performance in the Ford engine line-up. The shop where I dyno my engines had a 600 inch mud race engine on the dyno the other day. 1030 hp, with over 900 lb-ft of torque. Naturally aspirated.