Yep, I use 1.6 rockers on 1.550 o.d. springs quite a few times actually. I have a set of the 1.6 scorpions rockers I mentioned in my earlier post on a 383 SBC right now. Its wearing a set of 23 degree pro-topline aluminum heads with 1.550 o.d. springs and has no rocker arm clearance issues. I've used them on the dart pro 1's with the same spring set up without issue. Thier about $180.00 on ebay.