On the bang I would go with a real one 14 or 15 mmmm with the number 24 slide with the opening at the bottom modified for better idle otherwise it will run rich the needle should be the one with the two small rings on it.
The atomizers should be either a 2.19 or a 2.17 the jetting should pop in at around 72 to 76 depending on the air filter and piston port timing and Carter pressure due to running a stuffed or an unstuffed crank and the variables of the displacement of piston changing such pressures .
A reed intake cylinder kit will give better low-end torque because the reed will self regulate the flow valving.
On a 40 to 45 miles an hour build the best reliable two cylinder kits out there for a e 50 is the 62cc malossi kit.
My other favorite kit for the e50 is the treats alt kit which is a kit made for the Tomos A35 motor that has been modified for the exhaust to work on an E50.
The 44 mm version has just a pinch less timing in the 45 m m version but his excellent for mileage and lower r.p.m. torque.
The read will give you higher Carter pressures for snappy flow on small transfers.
Run best with a stuffed crankshaft.
The Thomas reeblock housing flows the best with malossi reeds.
Your timing should be at 19 degrees.
The head should be either a custom treats head or a stock hytorc.
Bring the top of the exhaust Port up a pinch 1 millimeter we'll do plenty.
Install new real Bosch points and condenser.
The gearing I would go with either 16x45 or 17x45.
With the exhaust the only two pipes I would go with would be either a promo or an estrell pipe.
The promos going to be loud as fuck and your neighbors are going to start shooting at you as you ride by.
The treats Center bleed estriol will give a slightly higher RPM Power Band and it will be much quieter especially if you get a center bleed version.
So with this setup either of the kits above will get you a really good Dependable all day 40-43 depending how fat you are. capable of 45.
Gear Slightly lower for better take off power and top cruising speed of 40+ with a little bit left for fun (edited)