45 degree for standard cam height, and 48 for raised cam normally. Having the option to choose, go with raised cam 45 degree cam bank angle. All it does is stand the tappets up more in line with the pushrods. Spreading always helps, but isn't necessary. Most shelf tappets will deal with .100 spread. .05 each direction. Straightening the pushrod is a good thing for as much as it's feasible. Like I said earlier a 48 will cause issue with the tie bar on standard type roller tappets. Jesel makes a center tie bar that works on a 48, but they're around 3 thousand dollars. They are worth the coin if you're stuck on the 48

As for cam tunnel, a 54.5 mm is 2.125 ford cam size. 55, 60, 65, 70 in my opinion is unnecessary given the rpm range these heads work at with normal cubes. You'll have rod to cam clearance trouble with aluminum rods anyway, so why compromise the rod with a huge cam core that doesn't help anything at these rpms. Go to a 1 inch tappet with a larger wheel than a .904 if you can, and run 1.9 ratio rockers if you're running shelf stuff.