I have a chance to buy my friends 2007 Silverado 1500. He has heavy duty tow package with different gears in the axle. He said its the same as the 2500.
Tow cap is 10,700.lbs.
My question: i plan to tow a 1997 Scarab 29 twin with triple axle hoss steel trailer. Trailer title says 1200lbs weight. The boat should be 6500-6700 lbs.
Even though i wont be over the tow limit Will this truck be adequate?

I cannot comment on the capacity of the truck however I doubt seriously that your trailer weighs only 1200 pounds. My Venture triple axle aluminum trailer (for my 29' Fountain w/twins) weighs 1700. With fuel and gear I'm betting your Scarab (nice boat BTW) is closer to 7000+ trailer probably closer to 2500 pounds. Someone who owns one of these trucks will be able to tell you about its ability to pull around 9500#s.

1500 with the HD package or just the wheels with 6lugs ?

if its the hd model look at the rear diff,the diff cover should have a oval shape to it instead of round..

I can tell you that I pull my 29 Scarab single with a 2003 1/2 ton Suburban. I did put a 6.0 in it and air bags on the rear. I pulled it all over the place on a 3 axle aluminum Venture until a couple weeks ago when somebody totaled the trailer for me. Now I am getting a big tandem steel probably a Manning so we will see how that works. Oh and the my Suburban has 285/75 17 tires so a little bigger than stock.

I think you'll be OK. I towed a 29 Baja OL on a steel Eagle tri-axle with a Chrysler Aspen. It was fine. Just make sure your trailer brakes work well. If he's your friend, hook it up and give it a try before you buy.

My aluminum tandem axle trailer with aluminum wheels,spare and disk brakes for a 28 A/T with a 10K GVW weighs 1560 lbs. (Certified Scale) Doug

I checked with my friend. He says the 1500 is a 6.0 liter Vortec max and he said when they put that motor in the truck they include the 2500 rear end. He did confirm it has 6 lug wheels.
He claims its got the same rear end as the 2500 and it has 4:10 gears.

As for my trailer....Its all steel so Im sure it weighs more than 1200. Why would they put that on the title for it if it isn't correct??

I pull a 32 Sunsation on a triple axle trailer.Truck is a 2010 Crewcab with the 6.2 motor.You will be fine with that setup.The trailer must weigh at least 2000 pounds.

i pull my boat with trailer with my 1/2 ton 2004 gmc my boat and trailer loaded around 6500 pounds pulls ok useing 3rd gear unless i am on flat ground has the tow button but i have no confidence when it comes to braking new 4 wheel disc brakes but i keep plenty of distance with the cars in front of me on the highway i am thinking 3/4 ton next year it works but you are on the edge