overheating 92 GMC V6

Have you verified the timing with a timing light. You could be off one or two teeth on the distributor from the RR - No way for anyone here to know just how well you marked it and just how close you got it re-installed to those marks. If you don't have a timing light you can just loosen the distributor and turn it about 3 degrees and retighten it. If my memory is right, advancing it will make the rpm's higher. Since you don't know whether it's off on the advanced or retarded side it doesn't matter which way you try it first, just don't forget which way you turned it. If the first 3 degrees doesn't make things better then turn it back the 3 degrees and then 3 degrees more in the other direction and try that. If that still doesn't improve things, and buttuming it seemed to run OK for both those attempts you can retry the whole thing only doing 6 degrees. Keep a close eye on the temp gauge as one of these attempts, esp the 6 degree change, is likely to make it heat up fast. Best thing of course would be to use a timing light and set it right. If it starts to ping, you know it's too far advanced.