300/ZF update

I haven't drove the truck much, maybe 1000 miles. It's a 92 F250 with the ZF 5 speed. Engine is a stock 300 with a 260H Comp cam, Offy C, 390 Holley 4bbl, Efi manifolds and the GM ignition module on a durasopark II dist. It starts great in any weather and runs smooth, drives out real good. But lately I have have noticed (as would be expected) that the 260 cam lacks good low end grunt. I have powered it out a couple times. You have to keep the rpms up and slide the clutch to get a load going. Like trying to pull start a 6.5 Chevy diesel or back up with a big load of fire wood. At some point I would like to swap on a ported head, chevy rockers and Isky mile-a-more cam.
to me the beauty of a 300 was always it's low end grunt, this engine is lacking that.