I just recorded one on our clubs 16 grader. The core from Cat was$3000 but got one from the local rad shop out of Milwaukee WI for $1600. Depends on size and core thickness.
75E501 - up equals 48A6883 - up is the 180hp (high horse). Your D7E 75E691 was built in the mid sixties not the eighties. You should be able to find a cheaper core.
Craig