that might be over cam-ing your 305. you might want to step it down a few steps. if you had more cid to eat up some of that duration it would be ok. if you decided to go with it i did notice it had the valve stem o rings. where are the seals? if your going that far to changed valve springs repleace your intake and exhaust seals too. i ran a xe274 in one of my 355's. that was a a bit over cam-ed. try finding a cam with a bit less duration. lobe sep is going to be very choppy at 108. 110 is very noticable. just my opinion