Production of B-17E ceased in May 1942.
Early 8th AF B-17 units
97th BG arrived 13 June, first mission 17 August (First 8th AF mission), last mission 21 October, non operational, to North Africa 18 November
301st BG arrived 9 August, first mission 5 September, last mission 8 November, non operational, to North Africa 26 November.
92nd BG arrived 12 August, first mission 5 September, became non operational training unit 10 October (until May 1943)
306th BG arrived 7 September, first mission 9 October
91st BG arrived 12 September, first mission 7 November
303rd BG arrived 12 September, first mission 17 November
305th BG arrived 12 September, first mission 17 November.
The first B-17E loss was on 1 August 1942, non combat, by the 97th BG, first B-17F loss was on 9 August 1942, non combat, by the 301st BG. Only the 92nd and 97th BG lost B-17E in combat, with the last losses on the 9 October 1942 raid on Lille. The 97th had lost its first B-17F on 6 September while the 92nd had B-17F when it returned to combat.
In 1942 the 91st, 301st, 303rd, 305th and 306th only lost B-17F, looking at the B-17E histories indicates any B-17E they had on strength were while in the US or for non combat uses. It is probable only the 92nd and 97th arrived in Britain with B-17E with the 97th at least starting the move to F models in September and it is possible the 92nd was selected as the training group because it still had E models, but to be sure you will need the relevant group records.
According to the B-17 histories, 5 B-17E served with the 91st, 40 with the 92nd, 65 with the 97th, 37 with the 301st, 34 with the 303rd, 10 with the 305th and 4 with the 306th (Some served with more than one of these units)