There is a guy who has shop down the street from you in Buford, GA (outside of Sugar Hill) that builds engines as well. People call him the Professor, but you can call him Mr.Johnson. Might save some money on shipping.
The advantage of a GMPP motor is the one year (from date of purchase, not from when you actually crank it up; so buy it last of all the parts you buy) warranty, that allows you to pull your car into any GM dealership in the the country and they will make it right or give you a brand new one.
I used to build some mean engines and I can tell you that an engine builders warranty is an insurance policy that says if you break it you fix it out of your pocket. You then file an insurance claim to get hopefully back the amount of money on the policy (but don't bet the farm you will get anything).