I've had a DOHC before - not a Marauder - so I'm totally on board for the 4.10s, but why the tune? Is it to correct the speedo?
I've hit 140, confirmed with GPS, with my 4.10s.
Stock 3.55s.
The tune is to correct the speedo, but more importantly to add more power and change shift points.
The stock tune shifts into OD at 36 mph, my zack tune shifts into OD at 47mph under light acceleration. Helps keeping your car in the powerband. Also the timing is advanced throughout. Short story, yes the stock tune is pretty bad.