I am looking at a used SP66 from HTT. The seller indicates it is an early model of the SP66. What is the difference between the older 66 and the new ones?

This particular turbo is about $400 cheaper than the newer versions.

Also, whats the difference between a sledpuller 66 and a pro-street 66

 

I believe one has a 10 blade exhaust wheel and one is a 11, and the prostreet has the wastegate spacer for better wastegating and is a71mm wheel

 

hey dieselfarmboy how does your 66 cool your mach 7's? any towing? surging?