I use Magnum heads with the stock rockers (1.6)on a 360 with a Comp XE268 cam in my Duster. Idle is quite smooth and low end torque is plentiful. With a 256 I can't imagine a problem. Set up your Distributor so initial is at least 16 Degrees (mine is 19). Up to the point of spark knock the most advance will give you more low end grunt. I even use the stock converter. With the 2400 converter it may appear to be weak on the low end but I doubt it. That's pretty close to a factory performance converter. My Stepson has a 2800 in his roadrunner with the 268 cam and complained about this until I had him brake it to raise RPMs before launch. Kind of like slipping a clutch. After he had some seat time with it, he was happy.
Drive ind enjoy it
Ron