The paradigm of shared spectrum allows secondary devices to opportunistically access spectrum bands underutilized by primary owners. As the first step, the FCC targeted sharing the 3.5 GHz (3550-3700 MHz) federal spectrum with commercial systems. The proposed rules require a Spectrum Access System to implement a three-tiered spectrum management framework, and one of its key functions is dynamic channel allocation (CA) for secondary devices. In this paper, we introduce coexistence-aware radio-channel-pair conflict graphs to capture pairwise interference, spatial channel availability variations, channel contiguity, and coexistence opportunities. We develop a super-radio formation algorithm to identify valid super-radios, i.e., a set of radios that can coexist on the same channel(s) via WiFi-like carrier-sensing mechanisms. With the proposed generic graph representation, we formulate CA as conflict-free max-demand CA with a mindemand constraint, and develop algorithms based on maximum weighted independent set. Preliminary results demonstrate good performance of proposed algorithms and benefits of coexistence.