Bolt diameter is 5/8". Get 2 nuts each for locking as these are not sholder bolts.
The Summit Racing PN is something like 0084.
Suggest you get the OEM rubber busings replaced too.
Replace the bottom thick spring leaf with an JCW add-a-leaf pack.
This will not increase heigth but will give you more articulation.

87 Raizer, 4.3V6, Mod TH700R4,231CHD, detroit rear and LSD front, bouncy seats, 2" lift and 32x15 BFG MT tires.