[REAL 1]

A new aluminum Shelby roller is $115,000.00. The wait is about 6 months last I checked.

You are not buying a well sorted aluminum Shelby Cobra for $105K new or used. A glass CSX yes.

As to the choice of motor. No doubt in my mind if you are doing a Shelby would be original 427SO first and a Shelby aluminum 427 second. Problem with the original motors is good ones are getting harder to find. My pick would be original assuming I could get my hands on a nice original block. In years to come they will increase in value IMHO and become even more sought after.

If you are going to track you car go with the aluminum block. I wouldn't risk damage to a valuable original 427SO. The new blocks are easy to replace.