I believe the T-bolts are the same length for both mono- & multi-leaf springs because the bottom spring plate meets with the welded spring perch on axle tube.
The plate/perch squeeze the pads and spring for fit.
I suggest using the OE bolts you have and slightly coat the threads with anti-seize and enjoy the ride.
Check nut every ten miles(?) until your confident they will remain tight, or are tight.