Ill just start off saying, it is way less expensive/easier to make a race truck go fast than a daily driver. A 6.70 is pretty quick, that is a mid 10sec quarter mile pass. While it is 100% attainable with a full weight daily driver, it will be pretty expensive if you want it to last round after round and drive it home every time.
Right now you are at a point where you need to either be happy where you are, or get ready to spend some serious money. You will need about 1200hp to run 6.70s at full weight, that HP gets you into bigger singles that arent the nicest on the street, and will require a restall on your converter. You will also be on the ragged edge of your stock rods, so plan on buying billet rods and if you do that you might as well go though and just rebuild the engine, go to a larger cam, better head studs, fire rings, ported head, etc etc.
Im not sure what trans you have, but at 1200hp you will need a serious 48re with oversized shafts. add about $4000 to upgrade the converter, and over shafts if you dont have them already. And you will also need a cage installed if you plan to compete.
This is why most people start looking for a race truck... You can expect to spend around $20k-$25k on the low end, to make your daily go 6.70s. OR, you can go buy another running truck for around $10k and swap the parts, putting your daily back to stock and HP parts on the other, gut the **** out of it, and go 6.70s with the same parts you already have at 900hp. (5500lbs @900hp should do a 6.70).
When it breaks, you winch it on the trailer and still go home and make it to work the next day.