Small Hughes cam in 318

Small is relative. A stock 340 cam is is the 1st step on the performance ladder. But if you compare it's specs to most performance cam lines it's equal to 250 ish cam.

I'm guessing O/D 4 speed ?
O/D does have a deep 1st gear probably making 3.91 too large. AJ can figure that out for ya.

CR and weight are your biggest enemy.
Pick a cam that works with your cr and everything should be fine.