After reading a few posts on this topic, I was wondering if it is necessary to have your valves shortend when using the Web Cams conversion spring kit. Thanks for your help!!!!

 

Measure the thickness of your old buckets, add shim thickness.
Then measure the thickness of the new buckets, shims, and any increase in cam base radius if you're changing cams too.
If the sum of the new stuff is more than the sum of the old stuff, your clearance will be effected accordingly. If smaller shims are available to get back the needed clearance, you're cool. If not, shorten the stems while the head is off the needed amount, or have the shims ground the needed amount at a machine shop.
FYI - smallest shim made is 2.00mm. Shims that came in my Web kit were 2.05mm. Even the 2.00mm was too big, because the Web buckets were .018" thicker than the stockers.