I am getting them part numbers from acdelco'* website.

Here are the choices for the 1998

Qty Req Qty ACDelco Part# Description
EMISSION / SENSOR-OXYGEN
01 PT919 CONNECTOR,INLINE-TO OXY SEN

4-WAY MALE BLACK
01 AFS109 SENSOR,HTD OXY(POSN 1)

IN EXH MANIFOLD
01 AFS123 SENSOR,HTD OXY(POSN 3)

And for the 1992

Qty Req Qty ACDelco Part# Description
EMISSION / SENSOR-OXYGEN
01 PT517 CONNECTOR,INLINE-TO OXY SEN

1-WAY FEMALE BLACK
01 AFS20 SENSOR,OXY OEM SENSOR

IN EXH MANIFOLD)(TYPE #20
01 AFS21 SENSOR,OXY OEM SENSOR

I just need help choosing which one to pick.

Here is the OEM (GM) part number for the front sensor, the one you're likely to need. Plunk it in at the AC Delco site for the AC part number. 25312203 This is for the '98.

Sorry, I don't have information on the '92. For that, you may want to search GMParts Direct for the GM number and then do the same search at the AC site.

why not try a Denso O2
Intense sells the Denso 02 for $59.99
ZZ Performance sells the Denso 02 for $89.99
Rockauto sells the same Denso 02 for $33.99
my last AC Delco O2 lasted for only 38,000 miles
first one lasted almost 90,000 miles
and i dont run leaded gas.
GM Parts Direct wants $62.00 for your O2 (p/n 25312203)

ROD