When I did the 1" BL on my 99,I was looking into doing 1.5"-2". I couldn't find any of the metric fine thread that would be long enough for the rear captive bolts. The stock front bolts should work fine in the rear up to a 1.25" BL. On my 87 trooper 1" BL, I reused the front bolts, but was 2 bolts short. I made some using althread and with two nuts with the outer one weld to the althread and the inner one to act as a jam nut.

'99 Trooper 3.5L->R150F->Duals->4.7->60/14b->38.5s
'96 Trooper DD