Reply to Old Magnet:
If the rails were the 3.91 in. height new and are now 3.75 in. that's still 50% worn. Hardly seems worth while to invest in pins and bushings. If it were 70% I'd say go ahead.
Joel59 - The position you're in, is a classic position of many crawler owners. Rails that appear to be too good to throw away - yet P&B installation costs that are high in relation to new A/M chains. Unfortunately, the situation is, that the low cost of new chains has seen P&B replacements virtually disappear, due to the sheer amount of labor involved in P&B replacement.
The bottom line, in your case, and with many others .. is that when the P&B's have been driven to destruction, as yours have, and the internal wear is severe (often being 130-140% worn) .. the counterbores in the links are very badly worn as well.
As the counterbore condition is a vital factor in P&B turns and replacements .. the severe counterbore wear in your links, means that a P&B replacement is a waste of time, anyway.
Once the counterbores are severely worn, the benefits of installing new P&B's are seriously degraded.
Good counterbores are essential to keeping dirt out of the area between the pin and bushing .. and to help prevent track "snakiness".
Seriously worn counterbores mean that dirt finds its way more easily into the area between the pin and bushing .. and the support area available to keep the track in line, is also seriously reduced.
As a result .. installing new P&B's in links with seriously worn counterbores is the equivalent of installing new front tires on your pickup, whist your steering is out of alignment.
The benefits of the new P&B's are seriously degraded by the shorter lifespan posed by badly worn counterbores .. as compared to the much longer lifespan of replacement P&B's, when they are installed in links, that have good condition counterbores.
My old track shop would not even consider replacement P&B's if the counterbores were seriously worn. I threw out many track chains with reasonable rail heights left, due to their badly worn counterbores. At $1300 for new A/M chains .. provided they are acceptable quality, and a recognised brand .. you are miles ahead on the new chains.
The most IMPORTANT factor in gaining the maximum from track life .. is keeping a close watch on P&B condition .. and EARLY P&B turns!
Cat hammer this point in undercarriage information books. I often turned P&B's at 80%-90% worn, because turning a good condition pin and bushing has the potential to give you much longer life on the turn.
Running P&B's until they are 110%-120% worn, and then turning them, will ensure that you only get about 60% potential life from the turn, as the weakened bushings commence to crack and break up, long before you get maximum life from them.