I looked it up. 360 2brl stock cam 71-74 is a split hydraulic. 410/412 252/256
75 and up is straight hydraulic. 410/410 252/252
I've seen many suggest that split cams do NOT work well with exhaust manifolds.
My 69 Barracuda Notch-Back had a stock 318 bottom end, a pair of regular smog type 1.88 valved 360 2brl heads with no porting, Edelbrock Performer Intake, Edelbrock 500CFM carburetor and exhaust manifolds. The 260 adv dur Comp Cams High Energy Cam I used worked REALLY WELL. 19mpg in town and a car that was FUN to drive ! NORMALLY I tell folks they are aiming too high with their cam choices but I think you are aiming a little low. If it must be an Off-The-Shelf hydraulic cam, I'm sure there are members here who can suggest a 260 adv duration grind with ramp characteristics that would work well in a 273. AJ. I see you hating on a 280 cam for his combination (I agree) but don't you agree that the 252 adv dur cam from stock 360 is aiming a little low ?