My 68 Barracuda was originally a \6 car with the 9" drums. IMHO, you should not drive the car on the road in traffic at all with those brakes, \6 or v8. I did for about a year and I can't count the times I scared the crap out of my self. If your car has the 10" drums you are in a better position to wait. I swapped in the 11" 73+ a-body disks in the front and 10 x2.5 drums in the rear before making the engine swap.
My car actually had the heavy duty suspension that included the .850" diameter torsion bars (most \6 cars will have the .830" bars) that were also used as the light duty sb bars and the 6 leaf rear springs. Again IMHO, even those bars aren't big enough for a \6 let alone a v8. Even with new shocks the car bottom over medium dips in the road and had excessive body roll in the corners. I upgraded to .890" big block bars (and lots of folks recommend even bigger) and installed a 1.125" sway bar before swapping in the v8. The brakes and suspension upgrades totally transformed the car, I can drive in traffic with confidence and the car handles on par with most new cars.
After the v8 was swapped in I upgraded to power steering and that was another major transformation in the way the car handled. Instead of feeling like you are at the tiller of a barge not to mention the thrashing of the wheel in a parking lot the car is now a quick and confident in transitional maneuvers.
It would be my recommendation to upgrade the brakes and suspension before even thinking about the engine swap and seriously consider power steering (if you don't have it). Your fun factor will be much higher if the car handles and stops on par with most of the cars on the road today. Doing the v8 first it will be hard to resist the temptation to use the load pedal and you could easily get your self into a position where you are planting your car into the back of a Civic that can stop in 1/2 the distance.