Well thats wall of text
If the sniper is similar to my terminator, make sure your fuel pump is handled by the sniper fuel wiring/relay. In my case, my pump would not match well with Holley wiring, so I left the Holley relay alone and its output triggers my existing contacter for fuel pump.
In regards to the breathers, if you can run the covers so the breathers are up front that is best IMO. Breathers up front then hoses to the rear and a catch can or just pan evac em. Less chance of oil sloshing out of em under heavy accel.
The oil sender, check if your block has a pressure port above the oil filter, if it does, just toss your sender there.