The 09 2500 hemi is the same engine as the fourth gen Ram. You will be fine towing a 7000 lb trailer, I would get a 410 ltd slip, I have the 373 in my 2500, and my truck pulls just fine, but a 410 will improve milage when towing.

 

I was told the 2010 has the active intake where as the 09 does not.

 

i had a '07 ram 2500 with the 5.9l cummins and six speed manual and loved it, wish i'd kept it. the cummins is a good engine, the problem is the politicians f'ed it up with the emissions requirements. if you're wanting a diesel, make sure it has the 5.9l cummins(early '07 or older), and not the 6.7l. the 6.7l has the egr and dpf, which is what kills the mileage when the computer goes into it's regeneration cycle and dumps fuel into the engine on the exhaust stroke to burn up the soot in the dpf- this also cranks up your exhaust temps to ~1500F at the exhaust tip. the only time it needs to go to the dealer for the dpf is if it cannot burn off the soot and gets plugged, which will happen as the ash made in regenerate mode will plug it eventually anyway. the 6.7l has the exact same performance specs as the 5.9l, the only reason it has more displacement is to make up for the emissions equipment choking it. if you're going to get a diesel, i'd recommend either the 5.9l cummins, a 7.3l/6.0l powerstroke or a 6.6l duramax('06 or older). also, something to remember is that diesels are not really broken in until ~30k miles, and that's when they really start to run well.

 

Also worth bearing in mind that the HDs will not have one of the 1500's best features, which is coil springs. The cart springs of the HDs will remain on the 2010s, I believe, even though they are otherwise 4th gen (ie body, interior, engine upgrade).

Coil springs are not for everybody, but they make a HUGE difference to the 1500's ride.