lippy It doesn't matter if the block is make from plastic,( save this for another thread). Good machinist, good parts, and good maintainance will extend the motors life 3 fold. There are some more important things like, ABUSE. beat the crap out a motor all the time, it is going to come apart. There is something to be said about running seasoned blocks over new blocks. It doesn't matter what material they are make of. I have been running a Shelby block for 15+ years with 1 rebuild for a bigger motor. From 452 to 482 in size. 7 years on the 452 of 98% racing and no failures to block. I did have 2 failures of valve train in heads. 2 broken rocker shafts. Both broken at mount hole between #7  cylinders. Went with a Erson setup and no failures since. I did improve mounts for rocker shaft asemblies by going to time serts in the heads instead of helicoils. Other 2 notes are this, limiting rpms to 6,000 -6,200 max. Get gearing of the car with a 3.07-3.31, you don't need any thing more unless a small block would goto a 3.54. Trans, 5 speed overdrive with a 2.80's first gear and a .80's 5th gear. Forget HP and build torque motor. Here the last thing and IMO building an FE with a preoiler and running an #80 psi spring in an HVHP
oil pump. This is for a street motor with a little fun at times. This is also with a storker kit of BBC rods in the bottom end. I have lived with a #100 pound spring for 15 years. Warming up the motor is important before driving. Having
oil pressure before starting IMO is also important. I am running a BBC rod bottom end. You can go any way you want from building a great 390 in iron with side bolts for the caps to a 527 aluminum beast. Paint the motor and no body will know. Build the motor on paper with the parts you want and we will see what power comes for this. Shelby block are built over the top. The engineering is unlike any other motor for strength and power limit,( about 2,800 hp last heard ). You can save money by buying a 390 and boring it to a 445. This will give you 500/500 at the crank and a hand full in the drivers seat to start. After this you may want to try something bigger. I can explain how different my car was to add another 150 hp and over 150ft of torque to it. This is crank numbers. Rick L.