Honestly, my well-tuned....M103 with a fairly low mileage bottom end, and a fresh top end has oodles of power (even at 5500ft). I believe it is very close to the factory spec'd 7.5sec 0-60.
I can't wait to take it down to sea level. Not sure why people bag on the M103 so much. Honestly the published 0-60 times for the late M104 engined cars are slower than that of the early M103. Especially with first gear start, the 300E is a joy to drive. IMO, the M103 redlining sounds ten times better than an M104 under the same circumstances. No, it's not going to blast people from the line. But 20mph rolling starts, it's going to take something with considerably more power (or less weight) to put it to shame. The M103 loves to rev and I think some people are afraid to drive it hard, but that is where it performs the best. One of the favorite parts of my usual commute is a ~1/2 mile considerable up grade portion of highway, punching it at 55, and by the top of the hill I can just touch 100mph.....it's quite fun. I think many people don't realize how nice a proper low-mileage/maintained 300E engine is.