Massive multiple-input multiple-output (MIMO) receivers with 1-bit analog-to-digital converters (ADCs) are a promising solution to reduce hardware cost and power consumption. However, employing only 1-bit ADCs introduces severe quantization distortion and degrades the performance of channel-coded systems. A practical compromise is the mixed-ADC architecture, where a subset of antennas employs higher-resolution ADCs while the rest use 1-bit converters. In this paper, we study the optimization of mixed-resolution ADC allocation under bit-budget constraints for LDPC-coded massive MIMO systems. Each antenna is equipped with either a 1-bit ADC or a bhigh-bit ADC, with bhigh ∈ {3, 4, 5}, and the total number of quantization bits is restricted by a budget Btotal. The decoding threshold is evaluated using protograph extrinsic information chart algorithm (PEXIT) analysis. Numerical experiments for 16 × 64 and 32 × 128 MIMO configurations indicate an efficient operating region at approximately 58% of the maximum budget, corresponding to only 6.25% of high-resolution antennas. Under finite bit budgets, the 1vs3 mixed-ADC configuration consistently outperforms other mix types, delivering the lowest decoding thresholds across all simulated budgets while maintaining substantially lower quantization cost.