Cam lift ?

I think you'll need more gear but it will be worth it if you really want it to haul ***! LOL
My 69 dart swinger 340 4 speed and 3.91's ran like a raped ape!
Clay Smith solid cam 258* at .050", .525" lift...mildly worked X heads with roller rockers and torker II 340...tires were 245/60r14....
The 3.91 gears were the least gear I could run and I hated it in the parkin lot.
Yes, I was running more duration, but on a bigger engine with a lot more gear...