What is the largest Outside/Inside diameter valve spring you can use on stock 906 heads before you have to cut down the valve bosses? The stock I/O diameter I beleive is 1.380"/1.020". And these Lunati's(#73815) are 1.500"/1.086". Am I gna need to cut the bosses down to use these? Anyone use these springs. They match the cam i just bought and i want to use them.

Not sure what you mean. If the spring is a dual spring, you have to cut the step out of the spring seats and you need the smaller positive seals so the guides need to be trimmed. This will also allow for greater lift due to retainer-guide clearance. From what I've seen, Lunati wants all dual springs for it's VooDoo line, and all those need the mods above.

These (73815's) are single w/damper. Not double springs. So im not sure if i need to cutem or not?????

Ah. They'll clear the step for sure. But I'm not sure on the OD... and you are getting the matched retainers, right? Stock wont work well with them.

yes sir! Got the retainers too!