I still have my 1995 Volvo wiring manual TP 3907202, showing the instrument cluster in detail. google search for 1998 c,v70 TP3932202 yielded the newer wiring diagrams. comparing the two there looks like only a couple of changes to adapt the newer cluster. yes signal from crash sensor is on the same pin B3. B15 is spare on 850 for SRS they moved the input signal from connector a:18 (pwr relay 2/31) to b:5 (ignition switch X pin) all other SRS connections are same. and for speedo, they disconnected a:3 from the analog speed sensor (7/33) and moved it to connect with pin 6 of ABS connector. google search shows 850 and s,v70 abs modules have same part number 10094604023, 9140773. with these changes it appears the 98 cluster could be made work in older cars.