Go with the 360 and leave the 340 for a restore.
If you are going to do much at the track leave the sway bar off. Limits front end movement.
OEM disc brakes will also slow the car as they have a constant drag and are much heavier than the drums. In fact drums will stop you quicker than disc up to a point but discs are more fade resistant. Drum shoes have more surface contact and the rotation of the drum on the shoe pulls them tighter into the drum. Disc's rely on squeeze on a rotating rotor.