Before the tech stopping was broken, you would want to fly the ULH route with a 764er, since it is super fuel efficient. That route would have done just fine with 764 tech stopped.
But now, you are probably going to get well below 200 pax, and it is probably not going to be worthwhile. What you can do is just sacrifice one aircraft for ~6 months , have it fly the route on just a 2-3 days that you can fit on the schedule, and wait for the RI to build up, and then you can re-evaluate. That would be a lot cheaper than getting another fleet type. If your test aircraft does not make much money, then probably just don't fly the route.