2D nearest-neighbor quantum architectures for Shor's factoring algorithm may be accomplished using the form of three arithmetic building blocks: modular addition using Gossett's carry-save addition, modular multiplication using Montgomery's method, and non-modular multiplication using an original method. These arithmetic building blocks may assume that ancillae are cheap, that concurrent control may be available and scalable, and that execution time may be the bottleneck. Thus, the arithmetic building blocks may be optimized in favor of circuit width to provide improved depth existing nearest-neighbor implementations.