Eh, someone in a big truck shop swayed me away from blocks a long long time ago.

For $150, the spring shop added three leaves to a F250 spring pack, new bushings and new shackles and added a 3 inch lift. 20 years later, no complaints. My cuzzin with his lifted K30 would go off roading and likely due to improperly torqued u bolts or rounded lift blocks, would spit a lift block out and mangle stuff once a month or so.

Spring shop had nothing good to say about imported 'brand name' helper springs, had a pile in the back for scrap.

Price just to re-set and re-arch springs last I checked was $40 a side.

On the cheap you can re-arch your own, you need a stump, a buddy and either a plain or tapered sledgehammer. Springs are formed and re-formed cold. Keep the spring moving and each blow will add a little more arch, arch the entire length of the spring, once you have say an extra 2 inches of free arch, take that leaf, lay it on the floor and chalk trace the curve, now match all the springs to that curve. A little sweat and you're done.

Also, on topic, a spring shop will form you custom square or rounded u bolts for a few dollars each with nuts and washers.

 

The 2000 F250 4x4 I used to have came with 4" blocks on the rear from the factory, so they can't be all bad if Ford uses 'em.

 

You are correct, some F350's had 6 inch blocks even, but you could have them swapped out for 2" or 4" if you needed a lower 5th wheel height.

Even 6 inch will get rough off road causing your leaf springs to wrap up into an S shape when you dig in, this is felt as lots of wheel hop. Bigger blocks, more hop. re-arched leaf packs are a good way to go.