What kind of pistons did you use? Did you measure piston to valve clearances to make sure you are having contact there?

If the edelbrock heads are the magnum replacement part number you may have pushrods binding in the tunnels as the roller cam A engines have different pushrod geometry due to the taller lifter.

Did you fill the lifters before installing them? I've done it both ways and seen it recommend both ways. Rhoads and some others recommend submerging the lifters in oil and working the plunger in the bore with a pushrod until bubbles stop coming out. I've seen others recommend installing them dry for less initial pressure on the cam lobes. They take longer than you might expect to pump up from bone dry and sound like hell until they do.

good luck, let us know how it turns out.