It shouldn't be a big deal. Most aftermarket SBC350 gaskets are 4.125" in diameter (on a 4.000" bore). This does slightly reduce the compression ratio as there is dead space between the head and block, but most people ignore it. Just pay attention to deck clearance and gasket thickness to keep your quench good (.040-.050" total).
The bigger problem is using a gasket where the diameter is smaller (like when you are +.060" and use a std gasket), the extra material dangling in the cylinder will get hot and cause pre-ignition.