Phil, didn't you say that you're running the Isky 301333? I know the LSA is 112; however, I've not seen the cam card. Overlap? Does your 55 Tbird have power brakes? Someone I know is building a 312/w target of 300 HP. I told him he'll probably need 228 degrees duration @ .050 to get there/w G heads, but he has power brakes. I'm thinking the 112 LSA of the 301333 will provide enough vacuum for his brakes. 

I have run both the Isky 301333 and 301444 camshafts in my Y-Blocks. The 301444 is what I believe most people call the E-4 camshaft and it's fairly mild. I am not a cam tech, so all I can comment on is my perception.   I have never run power brakes in any of my Y-Block cars, so I have no personal knowledge of that combination.  I suspect the 301444 would work OK with power brakes.  The 301333 is a different animal. It has a noticeably more ragged idle.  It's been some time since I put a vacummn gauge on my engine.  As I remember, it holds about 14 pounds at idle.  Isky told me the 301333 will work with an automatic transmission. I am not so sure. Possibly if you had a loose converter?  If you put this cam in a heavy car with a lot of accessories, I think you would be asking for trouble. My car is light, no P/S or P/B with a manual transmission and  4.1 gears.  My little Tbird is a hot rod, so I love the sound and performance of the 301333. Mid range torque is awesome.

Thanks, Phil.