test2.py

w_max = 2000

w_export = 507


export_ws = {}
# try all heights of crop rectangle
for w in range(w_export, w_max):
    h = int(w * 2 / 3)

    # now scale to export size with actual aspect ratio
    h_export = int(w_export * h / w)

    export_ws.setdefault(h_export, [])
    export_ws[h_export].append(w)

for h in export_ws:
    print('%s export height with these crop rectangle widths:\n %s...' % (h, export_ws[h][:10]))