There is still chrome underneath the carbon buildups which I've removed using acetone and scrubbing gently

 

Thats the middle iron, not a housing. The FSM has specs for checking the wear. It's hard to tell how badly its grooved. They can ground down to get flat but that removes most of the nitride finish, so it will wear much fast without t hat finish on it.

 

to be fair, that's what it's called in the FSM. All the irons are "side housings"

The factory manual has tolerances for wear, you'll need a dial indicator and feeler gauges to check. foxed.ca for manuals

I haven't used them yet, but some people on here have sent irons to Chips Motorsports, they do resurfacing and renitriding. https://chipsmotorsports.com/

 

I'd be surprised if it's economical to resurface a first gen iron. Resurfacing is not cheap. Definitely check the wear yourself though and if it's in spec it doesn't need any work besides a good cleaning