6.2 Diesel problems

I have a 1982 6.2. A while back, the accelerator started acting like it was sticking or binding. I could press it about a third of the way down and it would hit a stop. Then I could really stomp on it and it would go on down-- usually downshifting to first gear- and speed up ok. I first attributed it to the cable sticking. But after I replaced it the problem persisted. Last time I drove it, it got much worse. It would only idle, no matter how hard I pushed on the accelerator, then occasionally it would get power and speed up and run ok until I would have to slow down due to traffic, then it would do the same thing, Finally made it home . I am assuming the injection pump is goimg out, but would like any info/advice I can get from the experts. If it is the pump, can it be repaired, or should I just get a rebuilt one? BTW, I think the engine has about 200K on it. If I remember, it had about 140 when I got it, and I'm guessing I have put about 60 since I have had it (speedometer doesn't work) Thanks Larry