Crunch the numbers...and find out how much the torque convertor is slipping. Are the 4.10's pushing the cam past it's useable rev range?
I doubt it is slipping at all. It is the stock torque converter and only flashes to 1500-1700 rpm; it was run unlocked. The 4.10s are perfectly matched to the transmission gearing and engine RPM/stock cam, I've tuned the shift points so that at peak RPM, ~6100, it drops back down to MBT @ ~4200rpm.
While I've never dyno'd the car I used this chart as my jumping off point when doing the calculations:
Our powerband may be a little longer than this one as the cats were removed and the exhaust was a bit more free flowing (cut out), but it was close enough as a reference.
I should mention that the transmission was left in drive and that was the computer making those shifts, not me (I just programmed them). You can see the results in the attached chart from the datalogger. The car seems to be a little lazy on the 1-2 shift however it didn't seem to effect acceleration (MPH - green line), I'll see if I can't find a mechanical means of speeding that up.
At any rate the only way this car is going to get quicker/faster is to do a converter, add sticky tires and raise the rev limit... and I just can't justify the benefit to taking the ease of driving this car out of the picture for a few more tenths, even if it puts the car in the 11s. Which is very probable.
I definitely love this car and its potential.