Im not entirely sure of your capacity seing as you have a 700r4 and 3.42 gears.
My truck is a 95 c1500 with the z82 trailering package, 5.7L, G80 positraction rear diff with GT4 3.73 gears in it, and with the trans and engine oil cooler and according to trailers.com the towing capacity is 7500...