The 7188 and 7180 were based on the 1100 system (more finicky gas system than 11-87) and according to Dockery, the components necessary to make an 1100 into a 7188 were a full auto trigger assembly and the barrel with bayonet mount and mag extension. I'm not sure of compatibility of the 1100/7188 with the 11-87 in regard to the receiver and gas system (probably not compatible). There was also a change in the original carrier latch assembly and some other internal component because of jamming problems when the 7188 was fired from the hip or while canted at an angle. I know the modification was patented and I could look into my books for it.
Is it possible to email you the photos? I'm not familiar with posting pics on this board, plus I be able to scan them in and adjust them. I would be able to send them out around Thursday evening, if you want. Is your email address on the profile correct?
I know mine is missing a "1" before the "@" character b/c of a slight change of address.
Glad to find another afficianado of the autoloader shotgun. BTW, have you seen the Remington 870 Mk1 Shotgun? Basically its an 870 slide action with a the extended and bayonet mount/support bracket. Scattergun Technologies has a close relative of it called the Military Model, except it has an 18" (instead of 21") barrel, ghost ring (instead of the more traditional v-notch and ramp sight), and synthetic (instead of walnut) hardware. Having a clone of that and a clone of the 7180 (semiauto) would make my day.