My guess would be a very unbalanced car. Those rotary engines are light. Dropping in a heavy v8 has to mess up the driving dynamics of the car, though there's probably no doubt it's fast.
My guess is you have no idea what you are talking about. The all aluminum LS1 weighs very close to the iron-blocked rotary motor, minus turbos, intercooler, etc. The weight balance is actually closer to 50/50 because the LS1s weight is concentrated further back towards the firewall. Put simply, 400rwhp in a 2700lb with 50/50 weight distribution = a wicked awesome track beast.
Here is a weight comparison of a Stock RX7 and an LS1 RX7, both cars with the same interior options.
Wait what??? LS1 in a rx7??? Tell me more about this.
Pretty easy project really. Cammed LS1 with longtubes, otherwise stock LS1. 391rwhp.
Dyno video
http://www.youtube.com/watch?v=DQpD5kgdNBo
That location looks familiar, is that Nederland, CO?
Not sure of the actual town name, its just outside Boulder. I parked next to that lake/dam and did a little hike while visiting Boulder. I live in St Louis and that Durango has made the trip to CO, usually Keystone/Breckenridge, more times than I can count.