Second in line. I don't believe it will fit your '94, you need the AMR 2772/RTC7713 which fits '93-95 RRC and DI up to '98, it has two connectors which plug directly into the back of the radio, looks like this:
'90-'92 used the RTC 7668/RTC 7649. Couldn't find a pic of the back, but it has a sort of ledge on the back corner which the plugs connect to from the top and of course they're different from the later connectors so it's not plug 'n play.
1991 RRC 4.2, R380, LT230, TrueTrac, Detroit, sliders, 33s, blahblahblah....
1994 RRC LWB
1994 RRC SWB
1995 RRC LWB 25th Anniversary Edition
1995 D90 project