Been there done that,in 1998 I was paid to fit a brand new 8.2 Chev Rat motor into a 110CSW.It was rated at 480 BHP and 550Ft lb torque.Not a bad job as I removed a 406 mouse motor from it.The gearbox was a Th400 3spd onto a LR transfer box.RR classic axles.
Still one of the quickest cars I've driven,at 100mph you could floor it and it would kick down to second and accelerate - properly.It already had lowered springs and handled very well.Stopping was more of an issue - you could only stop once from over 100,then you had to let the brakes cool down.One prop uj was all the trans had in 2 yrs that I looked after it.
At 120mph there is a about a 1in gap at the door tops as they get blown out !
It was great fun,really enjoyed the experience of doing and driving it - esp as I never put petrol in it.Oh,about 3.5-4mpg gallon was what he reckoned he got.