My block has been drilled and tapped for the longer ARP main bolts. I am using the Canton 351 stud kit to mount the windage tray. The threads on the studs are the same length as the factory 312 main bolts which is shorter than the current ARP bolts so they won't go all the way in the block. Will this be a problem? I considered threading the studs further to get the studs all the way into the block  but am concerned if it will weaken the stud if I can even cut the threads with my die set. If I can't add threads I may need an additional washer on the stud nut tightens down properly or a thicker washer which shouldn't be a problem. 
Canton recommends using loc tight on the studs in the block. They don't say which loc tight so I am thinking blue incase I ever want to pull the studs later on.. My last question is the torque specifications for the nuts on the studs. Are they different than for the ARP bolts and if so what torque should I use?  Never used studs, always used bolts so not familiar. Canton says use 30 wt oil on the threads. 
I'm also curious as to what kind of horsepower increase to expect. I see anywhere from a 5 to 20 horse increase is possible with a windage tray but I'm thinking more like 5 to 10 horsepower.