I'm going to be adding some lights to my truck for my headache rack, under bed rails, etc. So being as its a PITA to find places to splice for power, I want to make a fuse box somewhere under the bed of the truck.

What would be the best way to go about doing this. I'm tired of splicing into factory harness. I'm guessing its just a matter of buying a fuse block and connecting it directly to the battery, or that Red Box on engine compt.

I'm also going to add a Fuse Block thats for ACC. only.

How about this one:
http://www.sealedfuseholder.com/

I'd suggest you look at the Painless Cirkit Boss Aux Fuse Block. I've been using the fuse blocks for the last ten years. The kit is extremely well made and has provisions for 7 circuits, 4 ingition hot and 3 constant hot. They also have a kit with all 7 ignition hot. Additionally, they make kits for inside the vehicle and waterproof ones for outside use. This is one of the first additions to any vehicle I purchase. They sure make installation of electrical components easy. Prices range from about $50.00 to $70.00. I'm sure you can find less expensive alternatives but I doubt you can find anything much better.

Your local NAPA should have a few different kinds in stock too.