I have a 2003 F-250 4x4 with a 6” lift (rear blocks/lifted front springs). I have 35s on it, so I want to drop it down to a 4” lift. However, I want to maintain a high towing capacity, but none of the springs I’ve found say the load rating, or they lack the information to calculate the load rating. Does anyone have any recommendations for lifted springs that are still able to tow 10k lbs+? Or does this just not exist and I have to use blocks?

 

There probably aren't any. A general rule of thumb is that when you lift a truck, regardless of how you lift it, you typically lower the towing capacity. Therefore even with your 6" lift you probably shouldn't be pulling heavy. Will it explode? Probably not. Are you at a higher risk for things to break over time? Absolutely.

 

What 99 said is pretty much spot on, big lift and big tires cut your tow capacity down. Might give BDS a call or a specialty spring shop like Alcan spring in Co and pick their brains. If you go with 4" blocks Id like to say I was extremely happy with a recent purchase of a 4" block set for my 99 F250 that came from RediLift. I got mine off amazon and they were $190 IIRC. Id also like to throw out not to use Wulf suspension. I ordered some late 99 parts in error, cancelled that order, and reordered the correct parts. Billed for both an been 40 days now and still NO refund or credit on my MC card for the error order. I gave up on trying to contact anybody as well as the never answer.

 

I'm going to disagree a little bit. while lift springs lose their spring rate, you can still haul heavy with the right setup. I do not know what all is available but I use stock springs with a kit from PMF suspension.
I have 5" tapered rear blocks and 3/4" ubolts. front uses a hanger kit. I run 35's which actually have a higher load capacity rating than stock tires. stock suspension, so no change in capability.
My blocks have the u-bolts go through them, so they won't move and are 100% secure.

dodge trucks come with 4-5" lift blocks from the factory if that tells you anything. you do need proper springs which typical kit's don't provide if replacing rear springs.also the typical lift kits have horrible block setups.

I have hauled heavy loads without issue.