Your truck reminds me of the Pro Stock Truck class that the NHRA
used to sanction. I miss seeing those trucks race.
My 220 lb motor scooter is not particularly stable at 50 mph, so you can expect a very
busy ride on a 50 lb motorized bicycle at that speed.
To achieve that speed, you will need to do a lot of reading on our racing sub-forum.
Our racers are the speed experts.