Although I've built up various blanks for use as catfish rods over the years, and supplied a catfish blank or two, I've only just built up a pair of Ballista catfish blanks for a customer.
Compared to the Torrix catfish blank, which is also 10ft long and rated at 5lb, the Ballista has a more through action. The build is to the customer's spec, but similar to what I have done in the past, although I'm not sure what I'd provide as a standard build.
A broad butt cap of some sort is essential (I like the Duplon one used this time), along with a decent foregrip or even a fighting grip. Not being a fan of full length Duplon I'd probably leave the blank bare between butt cap and a small section of Duplon behind the reel seat with either a longer Duplon foregrip or a fighting grip of either Duplon or Japanese shrink above the handle proper.