replacing rod bolts

Its not an issue of them wearing out but if you are modifing the engine with plans to rev it past the factory redline then the additional stresses can cause them to streach which can/will result in the nuts coming loose and/or the bearings/journals taking a beating.

Also, if the bolts have been stretched enough to yield them then the cross section has been reduced and they can't produce the same clamping force as before resulting in the first paragraph.

You have to remember that as much as the engineers would like to have designed the engine to live at 1000 HP the marketing and bean counters would have had their heads. So, the engines were designed for the target HP with an appropriate safety margin. The lack of finite analysis tools back in the day how accurate were those safety margins? Then increase the power with other changes any you can easily exceed the strength of factory parts.

Then factor in 30-40 years of unknown history of possible abuse it just makes sense to replace the two most highly stressed fasteners in your engine (rod &main bolts) and take advantage of 30-40 years of technology advancement with high quality fasteners for the rods and mains.