These cars were all rear wheel drive. They came with a few different engines. The MG A 1500, sold from 1955 to 1959, had a 1489 cc I4 B-Series making 68 horsepower in the early years and 72 in the later years. That's not horrible power considering the era and the low weight of the car. These are the most common of the MGA cars.
A high performance MGA Twin Cam was made in limited numbers from 1958 to 1960. Only 2111 were made, each with a DOHC version of the B-series engine used in the 1500. This car was discontinued because the DOHC engine was unreliable. The problem was fixed rather easily, but this fix was not discovered until after the car was no longer made. The fixed MGA Twin Cams around today run very reliably for a car of their age.
The MG A 1600 and 1600 De-Luxe was the second most common of the MGA's. They had a larger engine than the 1500 and some cosmetic differences. The De-Luxe got disc brakes on all four wheels.
The final MGA was the Mark II and Mark II DeLuxe, both of which are somewhat rare and highly collectible today. They had a bored-out engine that made a little more power than the 1600.
These cars are valued by many collectors. They have formed hundreds of clubs around the world to celebrate the small British roadsters and coupes. If you don't own one, but would like to, check out the listings on eBay. You can find some pretty good deals on there. There are also lots of parts available for these cars.