Not only that gun battle is from Finders Killers but everything else happening during the final 25 minutes as well.
Seven Devils on a Horseback is supposed to have scenes from The Law of Violence but I didn't notice any, possibly because I haven't seen The Law of Violence in years. Both by Gianni Crea again.
Go Away! Trinity Has Arrived in Eldorado is just re-used/alternate/leftover scenes from various Demofilo Fidani films cut together + new dubbing + some new scenes. This film (credited to Joe D'Amato) was mostly made in cutting room during few days. Bandits falling from rooftops were taken from Lobo the Bastard, if I remember right.
His Name Was King has scenes from Vengeance, the ones with Harrison riding from one place to another, mostly. No close-ups of characters are used.
Luigi Batzella's God Is My Colt has scenes from Even Django Has His Price. Stagecoach hold-up, attack to mexican village, big gun battle at the villa and scenes with bandits playing poker in a cave... at least! Some say that scenes from his own Paid in Blood are also used and that Paid in Blood has scenes from Even Django... but as I have not seen Paid in Blood I can't confirm this.
Roberto Mauri's Django... Adios is just 50 minutes(!) or so worth of scenes from Django's Here, Pay or Die! cut together with few short scenes from his own Wanted Sabata + some new stuff. Since I have not seen Django's Here... I can't confirm this but it looks like a cut-together film alright. His Corte marziale is a similar case using scenes from ...e lo chiamarono Spirito Santo & Bada alla tua pelle, Spirito Santo! + new scenes + new dub. Wanted Sabata has one scene which also apears in Django... Adios which doen't fit either film so it is likely to be from Django's Here, Pay or Die! Spirito santo e le cinque magnifiche canaglie has one scene with bandits trying to stop wagons with dynamite which has very different picture quality and shooting locations, so it's likely to be taken from some other film.