compression woes

[bob prohaska <bob@domain.elided>]

Hi all,

My '72 Scout II (V345, auto) has developed a serious lack of 
compression, but only in the two frontmost cylinders (1 and 2).
Number 1 shows about 90 psi, number 2 is only good for 72.

Squirting about a tablespoon of oil in number 1 raises the 
pressure to about 160, but it takes about 3 times that much
oil in number 2 to get a mere 130 psi. 

The rest of the cylinders are all between 145 and 160. So far
as I know the engine is stock, with stock compression, 8.28/1.

How credible is the oil test to distinguish leaky rings from
leaky valves? 

If the test is credible, what are the odds that a clean, well
maintained 345 will wear out its rings in 157k miles? 

If anybody's gone down this road before please share your story!
I don't want to tear the engine down needlessly, but neither do
I want to break anything, especially a valve!

thanks for reading

bob