I've made a set of lowering blocks for the exact application you are talking about.
I used the design that I saw from JTR's website.
http://www.jagsthatrun.com/Pages/Par...y-U-Bolts.html
(The version on the left)
I used solid 2" stock and drilled the bottom for the leaf spring "centering pin",... and then used a 3/8" allen head cap screw for the lowering block pin that will indicate on the flip kit bracket.
Just offset the indexing pin hole and cap screw to match the flip kit bracket,... and you will be good.
The picture below is for S10 lowering blocks.
So
your block dimensions may be different than this picture shows.