I'm going after my 7300/G3-275 right now with similar issues. I discovered I had the hard drive SCSI termination wrong... that made a huge difference. Just about to clean/regrease the CPU heat sink. We shall see.

So does anyone know of a good free memory test/benchmark/burnin utility for Classic Mac OS? Tons for Winders boxes but I can't find one to exercise my 7300.