Found videos of E30 supposedly with the E60M5 V10 engine
This one testing in a tunnel.. Check out the rev meter..
Check out the rate the speedo climbs..
This is how a stock E30 M3 goes from 100 to 250... (stock rev limit at 7,200rpm)
dyno video
Looks like there's definitely more than 1 E30 M3 with the V10 engine...