[garyd1961]

You need a stall to match your cam. Gears and weight will affect the stall also. I took a 383 out of an S10 with a 3600 stall and put it in my 70 C10 and it just wouldn't work. Way too much stall, sounded like my trans was slipping all the way through the gears.
With a small cam and these heavy trucks I would go with the 2400/2600.