This is a one wheel drive, scrub brakes. Its a varied 415 model Manco, great little kart, very sturdy. Yes its a 5.0hp Briggs.
Where do you ride the kart? If you're on street, they make slicks for the 4.10x3.50-5 tire, keep in mind that while you might want a drum for a brake assembly scrub brakes work they stop both tires equally. Unless you're planning on driving in the pouring rain they are cheap and very reliable.
Someone at one time put a small brace under your rear axle, these had a tendency to bow slightly over the years, you might consider a larger bar, even 5/8" cold rolled just so support it. We did that exact same many many times in the early 90's when these karts came in for repairs, here is one example of the same kart you have we had back at the shop for sale for Christmas this year.
Johnny, you've got a rod and 2 holes in each side of the rod, over time brake rods stretch from constantly force. You can take out some of the slack in the pedal and your brakes by moving each side in slightly, alternatively if you have a torch in your shop, make a s-bend in your rod, it will take out the slack and make it like new. The bending may not be necessary, but from your pictures I can see you have a large amount of slack between the scrub and your tire, it must need to bottom out the pedal to stop.