rod bearing sizing on high-mileage motors

[David Pertuz]

Since I am one of those people who can elevate procrastination to 
Olympic levels, I still have not replaced the rod bearings in my SE-R. 
They've been noisy (2500-3000rpm, mostly when cold) for a few k miles, 
but it helps that I didn't drive the car at all last year. But it is my 
preferred winter car since it's got the snow tires, and I want to do it 
soon when it's at least above freezing, before I take dying bearings too 
far and kill the crank.

I've done this on the JDM engine that I put into my G20, so it's nothing 
new, but I am a little unsure about what grade bearings I should put in 
there. The G20's motor was low mileage, replacement done as due 
diligence, same grades put in, whereas this engine has 220k on it.

I'll know what grade bearings it's got when I take the pans off, but 
what should I put in there? Same grade(s), or one size bigger (tighter 
clearance) on an engine with this mileage? For that matter, how can I 
practically measure the rod journals  without dropping the crank down, 
which I do /not/ want to do since it will drastically increase the 
amount of work. Do I even need to measure the journals? I would think 
so. I want to do it right so I don't have to unbutton it again. I'm a 
little worried as it is about having done it right the first time since 
I think I might have the beginnings of bearing noise on that motor too, 
30k later.

For that matter, why do they make noise at the RPM they do? And is there 
any other source that could be faking me out?

thanks,
David
Detroit, MI