You sound like my very first e bike. It was the same trike, and I put a 30 mph motor on the front wheel. It was stupidly dangerous, since above 15 mph it becomes nearly impossible to steer, even to jink around a broken bottle.
Runs in a straight line fine, just won't stop doing it when you need it to. And any slope of the road, you pull like hell down into the ditch at that speed. Plus, those rear wheels last about a day at that kind of speed too.
So, that 45 mph road on a wide trike, forget about it. If you have a better route you can go, bearing in mind an extra 3 miles on an e bike is no problem, you can get a nice front wheel trike kit for that ride. Its engineered for max power, yet a top speed around 15 mph. Get it here
https://www.ebikekit.com/collections/tricycle-kits
Or, on a bike, get a 30 mph capable rear motor kit. One of those 48v 1000w kits. Put it on a 7 speed beach cruiser, or any other bike with 7,14,or 21 speeds. A good set of rear baskets on a beach cruiser will carry just as much cargo as that trike.
You could use that other bike, but if you do, that one will need a front motor, because your only brakes are in the hub of the rear wheel.
This bike is painted ugly IMO, but it shows the good features you should look for. A very strong welded on rear rack, lots of room for a battery in the middle frame, chain guard, brakes on both wheels, and at least 7 speeds. ( avoid 9-18-27 speed bikes)
https://www.walmart.com/ip/Kent-26-Mens ... /392679122
The ideal cruiser is the Electra townie, though it won't have the rack.
Oh, btw, if you weld, then you could easily add disc brakes to those stretch cruisers. then add a bolt on 7 speed gear.
