I dont know if they are interchangeable but usually higher powered car's gearboxes (vr, 16v) have taller gears as they have more bhp and in a lower powered car the acceleration will suffer a lot if that box was fitted!
Easy check, look at what speed you're doing in 3rd at 3k, and we can check ours, i'll post tonight as can't remember off hand but if they are different you have a different ratio. I've a standard 8v so they should be identical (barring wheels sizes, but they dont affect the indicated speed at a certain rpm, only actual roadspeed)
I know in 5th im at 60mph and 2800rpm, 70 is 3k exactly, but cos its top gear all cars will be close to 1:1 or less so 3rd would be a better guide.