United MileagePlus (Consolidated) - Tailnumber on United flights from 1993-1994

I am looking for the tailnumber of a couple of United flights i did in my youth.
I know its very hard to find and maybe somebody outthere can help me?
Any information on these are helpfull.

Here are the flights:

1993-11-05 UA1725 GEG-SFO
1993-11-05 UA931 SFO-SNA
1993-11-09 UA1014 SNA-SFO
1993-11-09 UA1182 SFO-GEG
1994-04-12 UA736 GEG-DEN
1994-04-12 UA668 DEN-IAD
1994-04-19 UA343 EWR-DEN
1994-04-19 UA153 DEN-GEG

Best regards!
DM