There is an STC around somewhere that converts the 727 to a 2 man flight deck but I don't think anybody has done it accept the person that developed the STC.
The TAY conversion was not embraced by the rest of the 727 operators because of problems with using digitally controlled engines on an analog based airplane. If UPS was not as big as they are those airplanes would no longer be flying because the FAA came very close to recinding the certification. I believe they have now somewhat fixed the problem.
The digitally controlled engines had to have a "translator" interface between the analog system of the 727 and the engines. As with all translation things don't always come out right. The digital control units would sometimes read the static from the analog controls as a shut down order and shut off the engine, all 3 of them.
They figured it out as being caused by a series of events and airplane attitude
. They then convinced themselves and the FAA that one could control the chances of it happening again. Before they got it under control, UPS experienced several instances of triple flame out. One instance brought the airplane to 400 ft above the ground in the middle
of a city before they got 1 or 2 (I can't remember if the TAY conversion can climb on 1 engine, I know the stock 727 cannot) fired back up again and could climb.