RE: Is this a .46 electric motor..power wise?
A hot .46 can get to 1300 watts (about 1.8 HP) in flight. An Axi 4130 will go head to head with any .46 and some weaker .60's. The motor does turn at a lower RPM, so increasing the pitch is required. The Axi 4130 with an APC 12x6 and a 9S pack keeps pace with a .46 glow engine turning an APC 12x4. The motor has a little more thrust on the ground, but the glow engine turns about 4000 more RPM in the air.
If you went with 4120 size motors and 45 amp ESC's, about 3200 watts, you would not have to worry about cargo weight. You could use a 9S4P 12.8 Ah (4 x 3200mAh) pack and have nice long flights.
The smaller 550 watt motors should be fine though. It's a cargo plane and that's more than 100 watts per pound. But, if you can afford $1000+ for batteries go for it.
I'd like to see pictures when you get it done.