A failed EGR can cause engine management problems, but the RENIX doesn't get a signal from the EGR valve, and runs fine without it (and cleaner - I just wish I could plate the thing off and have done with it, but the Air Police won't let me...)
I think there is also a header or two that will work for RENIX - I seem to recall seeing them out there. I just don't recall who made them..
If you're not subject to the Air Police, you could easily get away with swapping out the entire top end with 1991-up (preferably 1991 to 1998/1999 or so...) and use a later header, later intake, later throttle body, and suchlike. If you go with a 1995 and earlier head, you'll have the port for the temperature sensor for the panel gage - I think it can be added to later heads, but I haven't gotten heads to check yet (I'm still trying to collect them - any donors?)
Since HEGO sensors are common, at least you won't have to get a HEGO bung welded to your header...