cheap mild 360 build

here's what I have:
1978 police 360 block re-ringed with factory bottom end and windage tray
1972 factory 340 intake and 1973 thermoquad carb
the block will be decked and honed that is it. I'm not buying new pistons
re-curved factory electronic distributor
factory cast iron manifolds(C-body drivers side) with 2.25" exhaust
The motor is going in a 76 swinger with an O500 trans and 3.23 gears
I would like to get 300 horsepower. now the questions:
I'm going to get a set of J heads reconditioned. what should I have done to them?
recommend me a camshaft. I want the car to run on 87 or 89 octane fuel. any tips and/or suggestions are greatly appreciated.