loss of oil pressure on 93 TC

Just received 2 Lincoln TCs from an older friend of ours ........ one is 2000 Sig. and the other a 93 . The 2000 runs and drives perfectly , the 93 starts and drives great but will lose oil pressure rapidly . At start up it's at 50-60 psi and and slowly drops to about 35-40 once warmed up . once it's warm and you drive off it drops drastically to 0 ? The other day when i picked up the cars I started the 93 and it ran for about 30 minutes and never dropped below 30 psi ..... would rev it and the psi would climb to 45-55 and back down to 30 at idle . Today I tried to drive it and the pressure started at 55-60 as usual and dropped down to 30 once warm and then after I drove off is when it dropped to 0 ? Engine has 94,000 on it and has been well maintained oil is clean and full . Any hints as to what is going on ?