Originally Posted by alcjphil

At some point old stuff wears out and is replaced, this seems to be what the OP is doing. The rear wheel has already been upgraded to a 9 speed cassette from the original freewheel, so this step is entirely logical. What the OP expects to gain is keeping the bike up to date. It isn't unreasonable to change a crank on a 30 year old bike. While doing so it isn't unreasonable to buy a component that is current.
I am an old guy too