Good grab old chap.
I've established that this aircraft would have definitely had the staggered, plain-window waist gun positions, and may well have still had an 'open' radio room gun hatch. The latter wasn't enclosed (on Vega produced A/C) until the B17G-65-VE, starting with 44-8401. But of course, it could have been fitted at Burtonwood, or other BAD or FMC, or even at unit level. By mid 44, most were enclosed.
The Cheyenne turret wasn't fitted in production on Vega A/C until B17G-55-VE, starting 44-8287, but again, many were fitted 'in the field' and of course at the United Airlines Mod Centre at Cheyenne. Most pics of 490BG A/C seem to show a Cheyenne turret.