Nathan, that "rebuild" might be good for many miles. It does not sound like it was what would be called a full rebuild, unless the cylinders were bored (and/or, honed and measured; and, the crankshaft was ground or measured; and, unless the head had the valves and valve-seats ground/dressed.
If I am reading the receipt correctly the crankshaft was actually replaced. There is a section of the receipt dealing with the valve seat replacement, certainly a good idea for our modern unleaded fuels, and subsequent valve job.
I know it wasn't over-bored because there is no line item for new pistons. It does have new rings so surely he would have honed the cylinders first! I'm betting the honing falls into the "labor" portion as this doesn't actually require parts but I wouldn't swear to it.
Honestly though I have no reason to believe that anything was done incorrectly or poorly. I haven't done a compression test but I haven't really had need to. It makes good oil pressure, fully warmed up at idle it's somewhere between 15 and 30 and with any RPM's at all it pegs the old '46's 30 PSI gauge.
It starts great, idles great, and runs great. It seems like all the major wear items were addressed in the rebuild and I know the engine has less than 12k on it since then. In my mind that's really low mileage, only just now getting full well broken in. But then again my view is skewed by modern engines that will go 300k with no problem.
I was just curious if they tended to only last 30 or 50k best case, or if they really were pretty robust. It's sounding like they're pretty robust and I don't have anything at all to worry about.
