I went with Keith Craft as he did a small block 427 stroker for me in the past that was awesome and many engines for friends of mine her in Texas.
My new Cobra I just finished has a Keith Craft 496 FE with a Pond Aluminum block with Edelbrock Aluminum Heads - Stage III by Keith. Solid Roller Cam, T&D shaft mounted rockers, steel crank and rods, Quickfuel 850 carb and lots of other cool stuff. Chassis dyno was 681 HP. I bought the motor totally setup, alternator, pulleys etc, flywheel, clutch/pressure plate and TKO600 trans from Keith. He set it all up including dialing in the clutch/bellhousing/trans alignment. I would not spend the extra money for a Shelby block as the Pond block is great and you could use those funds for additional items on the motor.....Keith has built a ton of these aluminum FEs and can work with you on what combination you want.
Additional pics of the motor and Cobra in my gallery...
