Against my better judgement, I ressurected a 1978 R100S engine which had set out for at least a dozen years. It had similar H2O penetration to one side and both rockers had developed rust. After a thorough cleanup, it wasn't really that bad. ended up just honing the cylinders as the rust hadn't pitted anything. The cylinders had a visual "stain" after honing but in "mic'd out fine and with some new rings / valve regrind we were on the road. While I was in that deep I went ahead and pulled the rods to take a peak at the rod bearings. They showed some discoloration ( maybe from heat?) but were probably OK, I changed them anyway since I was in the neighborhood. The one thing I over looked was a tiny pit on an exhaust valve spring which later caused the spring to break, slightly swallowing an exhaust valve and "dinging" up a piston.
Might be worth a deeper look before piecing her out. I think the R60 engines are pretty good candidates for rebore's (if needed) since there is a lot of "meat" on those cylinders.
Guess it really comes down to "how much can I afford...or want to spend".