I didn't really have a choice on using Jasper....when I lost reverse in Murray, KY, the Good Sam Roadside assistance folks wanted to take it to a shop in Paducah, an hour away, called Mike's or Scotty's or something. Never heard of them, no website, no info. There used to be a transmission shop in Murray but the guy retired and it closed up, now there are none. I got the name of a shop in a nearby town, but had the tow truck driver tell me they were no good. I finally got the name of a local mechanic in Murray from a guy here on RV.net (who lives in Murray), and so happened he was a Jasper dealer.
The unit wasn't cheap but I got to thinking, if the guy in Paducah gives me a 1 or 2 year warranty and it quits a few states away, what good is the warranty? I would have rather the trans been rebuilt by a skilled rebuilder, it would have been cheaper, but since I was unable to find the right guy, Jasper was a good plan B. The more I think about it, it makes sense since we're all over the country in that truck.
Anyway, you are in a different situation, not being stuck away from home, and I would think that any GM dealer would provide warranty service on a GM crate motor if there was an issue. I'm not sure that I would pay more for a reman vs a crate motor either, but with the level of detail that remans are done at these days I'm not sure there's that much difference between new and reman anymore. Not trying to sell you on Jasper as a better option, just thought it was worth looking at.
Was doing some reading on the Jasper site today relative to installation, and it cautions that if the engine has an external oil cooler (my 8.1 sends engine oil through part of the radiator, not sure about the 5.7) the cooler must be replaced when the new engine is installed. Ironically I just put a new radiator in my burb because the plastic tank that houses the engine oil cooler cracked and was leaking coolant.
I also replaced all the brake and fuel lines this spring, heavy corrosion from too many years of beach camping when we lived on Long Island.