Maximum speed with this engine on completely flat ground is around 110-115. It has gone faster, but it had to have been on a slope. I wouldn't say that the acceleration is that much slower. I have raced a stock 300SD W126 and was a good car length ahead, but that car still had a "tamper proof" ALDA and stock boost setting with no hint of smoke. Floored mine was a little hazy with 13psi.

Apologies again about the poor video quality, one of these years I may have to buy a real camera. The 1st and 2nd acceleration videos were on a downward slope, so they are faster than the flats (not much flat around here) and were from a rolling start. You can hear one of the back tires chirping on the 2nd video going round the corner under power. The aim was to show the max speed ranges for the gearing, I was making a video of the last drive of that car which is now retired after serving me very well. I bet that the 2.88 is a little more desirable, but the 2.47 seem to be easier to come by in the yards, or it was years ago.

The replacement W126 I am building will have a 2.47 LSD from a 560SEL, that one may be way too low for the OD 5-speed box... will have to make a new thread about that down the line and let you all know how it goes.