This guy in axtell has built 3 different gn motors for me and my dad. Before that, he built my dad's 455 motors as well.
Automotive Performance Machine/Barnard Racing Engines
931 Bays Rd
Axtell, TX 76624
254-822-1526
He knows what he is doing and gets a huge majority of the circle track business in the area. Due to that he may be a little overwhelmed, but he has a dyno in house and can do anything from mild to wild.
Dont know if that phone number is accurate or not, but that is one that I got off the internet.