I built my TD on the 1740# HF trailer. It of course has springs shackled at both ends but that shouldn't make any difference in using a 'lift block' to gain height. My build is 'over the wheels' so clearance was important. Total TD weight of around 1150# on a 1740# trailer so I figured a couple of inches over the tires should be OK. After a couple of years & several thousand miles I noticed a few (very few) slight marks where it appeared the tires had been making momentary contact with the underside of the wheel well top. No apparent damage to either the tires or the trailer body but I decided I needed additional clearance. I had on hand some 1" thick steel so I cut a couple of 'spacers' to same dimensions as the spring seats that were already welded to the axle. I'd never been all that fond of the lightweight (to me anyway) 3/8" (or metric equiv

) 'U' bolts that HF used on their spring/axle anyway so I had my son (who has a NAPA store

) get me 4 new 1/2" automotive strength 'U' bolts of sufficient length to accommodate the added height of the 'lift blocks'. Since the HF springs have a 'keeper' pin (bolt?) that rests in a hole in the spring seat, I used my drill press to 'machine' a similar recess in the top of each block. Was then a simple matter to raise my TD high enough (well supported by jack stands

) to unbolt the axle/spring, slip in the 'lift blocks', replace the old 'U' bolts, & torque everything up properly. The additional inch of clearance has worked very well through more'n 10K miles with NO evidence of contact between the tires & wheel wells.
Depending on how much more height you need, spacer (or 'lift blocks') should do the job for you.

