Honestly, the "best" alternative here would be to have all 60 trunks be 2-way and staggered across the 2 curcuits.
If your trunk numbers are 101-130 for the first PRI and 201-230 for the second, having your carrier setup incoming calls to go:
101, 201, 102, 202, 103, 203, 104, etc.
And outgoing calls in reverse:
230, 130, 229, 129, 228, 128, 227, etc.
This gives you control and some failure tolerance. Not all carriers or situations allow for this, but just getting them all setup as 2-way trunks would probably help.
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