Haven't been on GMT for a while and just saw this post. Am sitting in travel trailer at Crescent Bar near Qunicy WA, towed over from Blaine Monday which means up and over Stevens Pass. 383 charged up all the hills in third till we got to the last 3 or 4 miles of 6% and pulled it in 2nd, 3700 rpm at about 55 mph. Trans didn't get above 190 and engine hardly got warm. Simply no comparison with the old 350. 4L60e is holding up fine so far and most of driving on I-5 was in 4th and trans temp ran about 150, 383 likes it, so does the tranny.
What's nice is the torque, with the 350, to get started had to get the rpm's way up to get moving so made a lot of noise with little results. With the 383 starts out nice and smooth at low rpms and gets up to speed without making a lot of noise, that's what a stroker is for.. If I want to really get going, I go thru the gears manually and stomp on it in all 4 gears, gets moving quickly that way.
The builder, S&J Engines in Spokane, thought the horsepower would exceed 350, don't know for sure but its got a lot.