I actually have some really tired/borderline "WTF?!" stuff that makes really decent numbers with a comp. tester. "Tighter" engines will supposedly make the pressure with less revolutions/cycles or whatever, but I don't think it's really a good way to determine engine condition beyond a very basic "nothing terminally FUBAR"; the leakdown test is what you want to check for ring condition/wear.
I don't think it's at all unlikely that it might have 185,500 if it's a little tired--especially if the head has been off and it's been worked on or potentially rebuilt. The 250 in one of my trucks has several hundred thousand on the clock with bad cam lobes, smoking, extreme oil consumption, rolling down slight hills in first gear, etc., and it still made nearly the same numbers as my nice 250 using the compression tester; it also somehow still lights right up and runs great, despite all that. The leakdown test didn't lie, though; something like 20% for the good one, and IIRC something insane like 65-80% for the tired one (did I mention it's somewhat tired?
).
The problem with it already being previously rebuilt at .030 is that there's a good chance it won't clean up at 0.040 and you will need to bore it out more than that to clean the cylinders up. Not a big deal if you have another block that will go 0.040 and clean up, but it's just unnecessary potential BS IMO. I don't really see any potential benefit to ordering parts before it's even apart.
FWIW, I'll attach a picture of the 98,500 mile 307 in the '68 Impala I just bought. It's borderline unusually clean (besides the milky oil from a botched intake install), but it illustrates that 98,500 ain't a whole lot for close to five decades. This engine seems to have great compression (tight), lights right up and runs like brand new, is super quiet (no lifter noise, etc), doesn't have a bunch of blowby, and seems to have good leakdown numbers like it should. The car is also pretty much like new mechanically, with no play in the door hinges, no leaky pinion seal, gouged up/replaced brake drums, etc. The 350 with something like 100,000 on it in my father's truck is also still very nice. I think most people really underestimate how many miles the odometer in their truck has really counted off in the years past...