I'll enter the fray over IM gaskets/Dexcool, along with oil usage.
I have a '92 Bonneville, with 224K. In March of 05, I bought a GM Goodwrench engine, had it installed (swapped) and changed over to Dexcool. About a year ago, I noticed that my oil usage (first 2 years, changed it twice a year, using only Mobil 1) was up...had to add a quart in between the 6 month change interval. I'm now using a quart about every month (still sticking w/Mobil 1), depending on how my wife drives it This past weekend, i noticed my coolant resevoir low/empty....YIKES. I know these engines are known to go through IM gaskets. There is not a single drop of ANYTHING that comes from the engine/trans area...except water from the A/C evaporator. So i called my 'trusty' engine shop, got a quote on heads (~$295/ea) and decided to start the tear down this weekend. UNTIL I see all the fray over Dexcool. This car had about 185K on it using the standard Green stuff (prestone) and it NEVER had any IM problems (from 16K anyhow, as my folks bought it in 5/92 as a program car with that many miles on it). I bought it from them with 99K and it has been the daily driver, ever since.

Anyway, I think I'll be replacing the Dexcool with the standard green stuff after I pull the heads and have them rebuilt. (Yes, i've done all the recommended stuff, new PCV valve, clean oil, etc...but the oil usage still continues...I even changed out the valve oil seals this past Nov....and after an 800 mile road trip (didn't see any oil usage during the trip), it'* back to the same thing.)

I've heard that (sometimes) the EGR valve may contribute to premature IM failure (due to heat), but since the 92 doesn't have an EGR valve (the only year, I believe), I can't see any other reason for an IM failing other than Dexcool (no...even though my wife drives it, its maintained nicely).

Regarding this Goodwrench engine, this is the first GM engine i've had problems with. I've purchased 3 TARGET engines (2-3800,1-5700) over the years (yes i'm old and cheap) and have never had problems with any of them (A target is a service replacment engine that GM uses to swap out warranty work at dealerships, from what i've been told. But once the engine is superceded, as in the case of my '92 3800, GM wouldn't produce them after 1 or 2 years). Anyway, no more Goodwrench engines for me. If I ever need another engine rebuilt, I'll either junk the car or take it and have it rebuilt by my trusty engine mechanic.

I don't have any specific questions, just thought i'd through my 2 cents in and see if anyone has any comments. Normally, I don't like going into the engine (hence, i've always purchased a complete one), but from my vantage point, this doesn't appear to be rocket science. First time looking at a fuel rail...but according to the book, you just have to be careful. Thanks for your time.