All of GCs converted loco hauled stock used mark 3As, which were fitted with IC70 seats. Only the mark 3Bs had IC80s. Im confident that Grand Central use IC70s in standard class, and EMT definitely do, although I wouldnt be able to identify the difference in first class seating.
All Mark IIIs were fitted from new with InterCity 70 seats except for the Mark IIIBs. These were first class only, and were fitted, as stated earlier, with a revised seat based on the APT design and known as InterCity 80. The IC80 term was only applied to those first class seats in the 3Bs, although further developments of the IC80 were used in the Mark IVs.
The biggest difference was in the seat frame and recline mechanism. The IC70 reclined the seat back rearwards as the seat base was drawn forward to give the recline position. Therefore, when upright, you were not close to the table. The IC80 worked in reverse by drawing the back upright as the seat moved forward - a fair better design. The IC80 seats were also recognisable by the large stainless steel frame to the side and rear of the seat shell. Originally, the seat cushions were also of a very different shape.
When the Virgin refurbishment was undertaken in 1997-1999, Virgin wanted a common look, so the IC80 was given cushions of the same shape and style as the IC70 - and the seat was given the nickname IC75. These are what you now see in the Anglia vehicles first class coaches, all of which are Mark IIIB. The standard class seats and catering vehicle on Anglia are all seated with IC70 (except for the end of vehicle new seats added to increase capacity).
All other original remaining Mark IIIs with EMT and Grand Central contain IC70 seats, although I believe DB or DRS may have a couple of Mark IIIB firsts which may still have the IC75, and the three FOB vehicles sent to GW for the Sleeper used to have IC75s also (not sure whether they have been changed?).
Hope this clarifies
