First confirm you have a 24:1 box, as already mentioned it should be ~5.5 full revolutions from steering lock to steering lock. If it’s only 3.5 full revolutions lock to lock it’s 16:1 and would explain why it feels heavier.
When is this problem occurring? When sitting still or while driving? Remember that you’re only supposed to be turning the steering wheel while you’re moving/rolling. New cars with a power rack let you “dry steer” pretty easily, but manual steering will not and it’s not a problem, it’s just different. If this is only a problem when you’re stopped or going less than 10mph, it’s probably just normal manual steering. If you can’t turn easily while traveling at speed that’s a different story.
The steering wheel should be very easy to turn with the front wheels off the ground. If it’s not there’s a possibility that there’s an internal issue with the steering box or possibly some part of the steering linkages (pitman, idler arm, tie rod ends etc).
Do you know your current alignment settings? The steering effort is effected by your alignment. This isn’t likely to cause massive effort to be required, but it does make a difference.
