There is a pretty good difference between the two trucks but it just all depends on what you are going to be towing around. Changing gears are simple but if your not familiar i would let an expert do it. It will probably set you back $500-800 depending. And, a 3500 leaf will bolt straight up to a 2500 truck, but those leafs are usually pretty expensive, but really simple to install. Not really sure what the price difference is but it could be worth it to do yourself considering a 2500 is probably a bit cheaper, and it will be cheaper on insurance and registration compared to a 3500.
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07.5 Mega Cab 6" Lift, Recon Lights, Dual MBRP, Shibby Compounds, Studs, 90 hp sticks, ATS Tranny, Mag Dif Covers, BD intercooler, Reunel Bumpers, Edge JWA, MP8, all deletes