Broken Valve Spring - Which New One?

The fact one broke doesn;t mean what it has are inadequate. But given the lack of info on it - I agree with the "measure it" and get something that will work. You have toknow what the cam is to really get it right. If the heads are different god knows what's on it. You can also check the pressures of the others and see where they are. My guess is if you measure the pressures on the springs, and measure the cam to get an idea of lift and rate of lift, you may find the two are not compatible and you need more spring. Use of the car means nothing. The engine is either right or it's not. Broken spring to me says it's not and it's lucky it didn't eat anything further.