Replace pwr cord w/IEC socket on vintage gear?

Stltrains, You are mistaken. There is a right way and a wrong way to plug in vintage equipment. Without any other equipment connected to the subject component plug it into the wall outlet and take a voltage reading from the chassis to ground. Then turn the plug over and take another reading. Whichever reading shows the lowest voltage is the correct polarity. When vintage equipment is plugged in the correct way they sound modern. When plugged in the wrong way they don't.

Has anyone ever been shocked by an old refrigerator when you were a kid? If you did it was because it was plugged in the wrong way and there was too much voltage riding on the chassis. Turn the plug over and no shock.

It's not a matter of personal preference. There is a right way and wrong way.

There are a lot of classic power amps from the '80s, with captive power cords--Electron Kinetics Eagle

I've never seen an Electron Kinetics Eagle with a captive power cord. I've had7 of them, and seen dozens more and they all have an IEC connector.

I've installed IEC connectors of many vintage amps and never had an issue reselling them. Further, it's a tedious job - 1 hr labor is not a bad deal.

Rrog on vintage fisher amps/preamps ive bought and replaced out of spec original caps and resistors the sams and fisher schematics for those units shows the a/c plug feeding the power transformer power windings and service receptacles with no polarity marked hot or neutral and the instructions do not mention a right or wrong way to plug these units in. these power amps and integrateds have a so called death cap installed for the shock hazard you mention on fridges due to there super high stepup voltages. these units are late 50s early 60s built when life was simple and much better.

Marakanetz thats very true on the cost of iecs and the added connection but in the end worth it for better sound imo.

If that Heathkit is a tube amp without a protective cage, you do not want a grounding power cord for the same reason toasters and lamps are not furnished with three-prong plugs -- live parts exposed from damage have no bond to earth. Also, the grounded power cord can put the signal and chassis to the same ground, possibly causing sonic problems such as humming from ground looping. This really should be done by a pro.

Stltrains, I am also referring to vintage Fisher, Scott, Dynaco, Sherwood, Harman Kardon, Audio Research and any other vintage equipment with a non-polarized plug. This is especially important with mono amplifiers and preamps since it does affect the sound depending on how they are plugged into the wall. This is also true with vintage turntables and tuners.