If you can beg or borrow a pocket hole jig you dont have to predrill holes. I haven’t done a table top other than a workbench(Plywood!) but I have done cabinets and beds. The Kreg jig makes joining easy. A lighter stain colour would cut down on the grain marks, or a heavier application like an espresso stain. I will throw you a pic when I finish my table and show you what I mean.
Begin by cutting off a 10-in. length of the board and setting it aside. Rip the remaining 38-in. board to 6 in. wide and cut five evenly spaced saw kerfs 5/8 in. deep along one face. Crosscut the slotted board into four 9-in. pieces and glue them into a block, being careful not to slop glue into the saw kerfs (you can clean them out with a knife before the glue dries). Saw a 15-degree angle on one end and screw the plywood piece under the angled end of the block.
Your monster of a table is going to be HEAVY, so I strongly recommend moving it to its final destination in two pieces–lay a blanket down in your dining room, put the top on it upside down, then the frame upside down on top of that. Attach a couple 2×4 supports across the frame for good measure, then begin the frustrating process of centering the frame on the top. Once you have the top centered, attach your brackets–I did two on each end and three on each side. 

Just redid my dining room table with this technique and I an observation/suggestion others might find helpful. The boards did not line up well putting it together upside down, even on a flat concrete floor with me standing on the boards while they were screwed. I would have combined biscuits with the pocket holes to ensure a better alignment of the boards. Lots of sanding was required after assembly, and this might not be a huge deal with pine, but I used hard maple so it was quite a chore even with a belt sander. Also, be aware that the 1x2s around the edge may not line up perfectly -- I had to trim about an eighth inch from each side after assembly to get nice smooth, even edges. Not a big deal, but the top turned out a little smaller than the specifications I was give by SheWhoMustBeObeyed. Otherwise our table now looks great, and thank you for the post!