you said you were trying to add about 50 hp and more low end torque???
Here is my 40 year old 318 (1976), short block never taken apart. Home ported the worst smog 318 heads on earth, and didn't even have them cut. Threw in the cheapest summit cam kit (109 bucks cam & lifters), and put on a spreadbore cast intake with a squarebore 670 holley. No headers, 2.76 gears, stock converter.... Low end no problem with me... I found the best traction road (chip seal) we have for street tires... still no dice, still spinning up to 50 mph and backing off just a tad to get it to quit :D