Good deal on GTUs?

[RB25240kouki]

Recently I found a GTUs for sale. $3K. It has 154k miles, a series 4 "block" with everything else from the origonal seires 5. The seires 4 was rebuilt and has only 80 miles (since rebuild). Went to look at it and the car was on jack stands (big new tire foul up... too long a story to put here) so I didnt get to drive it. I told him I was interested but of course wanted to drive it. So I made an apointment to do so the next week. That morning he was going to do a break job. He went to test drive it to check the breaks and raced a honda in the process. BAM. Blew the engine (dont know the details). He says he over reved it to 9500 rpm. But I know why it blew. The series 4 motor has a redline of 7500 rpm but the series 5 computer was limiting the revs at 8500 rpm. So in other words he over reved it a lot then over reved the CRAP out of it and blew it . Now he plans to put a NEW sieres 5 motor in (But he said he also might put in a rebuilt series 5 but most likly new). And he is only going up $500 ($3500). Is this a good buy? Should I avoid it. And what should I look for on this car that might be wrong (common problems to 2nd gens and any "GTUs" problems). Well, I appicate any feedback. Mike