I’m building my second bench. I built the first years ago with wood from old machinery pallets – mostly oak and maple. Mortised the legs into the base, and pegged ’em with 1″ dowels. Of course, the legs warped a bit, but that made everything tighter and stronger. The top is 2″ thick Ash, one board cut in half and joined side to side. Wrapped a maple apron around the top, and I think I screwed the top from underneath to the leg braces. Solid. Over time, built a cabinet under for 3 drawers and a small cabinet door. Works for me.
My advice? Don't do this. If you have jointer and a planer, use them. If you don't, seriously consider using dimensional lumber that has already been planed and sanded. If you are going to try to clean up construction lumber by hand, using a hand plane is a lot faster and more pleasant than using a belt sander. Except, of course, that to do a good job of planing a board you need a solid bench to hold the board, and you don't have a bench, yet.
Chris I blame you for all these altars that are being built today and now you thinks we over thinks ’em–huh. You whipped the masses into a frenzy— now Woodworkers are trying to out pretty each other–out wood species each other –out Rube Goldberg each other. I made 2 benches in 30 years neither had a through dovetail but many were made on them and I have no idea but I would bet a dollar that neither weighed 280 pounds but they both had tons of wood on them. If you want the bench as a destination god bless but it was intended as a mean. Thats my rant I could be wrong

 6. The Complete Book of Woodworking by Tom Carpenter. Another great reference book you'll come back to again and again. The latter half contains a bunch of projects you may or may not end up making (I bet you won't) but the details covered in the first half are as good as any overview-style book I've come across. When I want to make sure my process is up to snuff when I'm working on a ManMade post, this is the one I check first. 

I marked the holes by putting a dowel center in the end of a long piece of 1" dowel. Run it through the holes in the base plate, and bang on its end with a mallet. Rotate it a bit and bang it again, and repeat. Odds are the dowel center won't be precisely in the center of the dowel, so you'll be making a small ring of marks. The center of the hole is, of course, the center of that ring.
I’ve built workbenches with more than 100 students. In every class, there’s one guy who wants to put a vise on every corner of the bench. Not because it’s a partner’s bench for two people. Just because he wants it that way. While I support your freedom to choose, I also don’t want to spend two weeks installing complex tail-vise hardware on your bench when we could be building furniture instead.
This bench suffers from no such limitations as it provides an incredibly solid and stable workspace, albeit in a somewhat stripped down version. In terms of performance, Sjobergs tops our list at providing 80 lbs of weight capacity. This is one of the more quantifiable measurements to determine the quality of a work bench’s craftsmanship. This is achieved by using thick pieces of European birch wood and working it without using lower end joints – like butt joints.