For what its worth i just ran into and was talking to for awhile at a local chicagoland chevey show, to one of the employees who works for the one lap of america Z07 owner and he was there with the car and that Z07 motor uses the awesome and very expensive C5R block. That Z07 car that one the one lap is AWESOME and the car is an 02 electron blue Z06 which looks like a trans am racer with its racing wing, etc. Also, it is true that MTI normal's Z07 motor is a resleeved alum. block and if you want an ironblock 427 like they built me then you just have to simply tell them that. I went with the ironblock b/c i like the extra strength of that block but wish it could be bored out as much as the resleeved alum block which now is being bored out to 4.125 and with the 4.00 crank is achieving 427 beautiful cubic inches!

Call MTI, they will build you what you want and will take care of you and stand behind their product 100%. You can't beat their 2 year 24K mile on their superstroker motors which you get if they do the install and tuning of their built motor! Best of luck!!

MTI 427 Roadster