The F1 uses an incredibly unique powertrain layout - the engine is ahead of the transmission, similar to other designs you mentioned, but the F1's transmission is mounted transversely making for a very compact package.
Here are some images to give you a better idea:
In the shot above, the transmission isn't really visible, but you can see how close it sits to the back of the engine, running long ways between the two rear wheels.
That's a rare shot of the guts of the transmission.
The shot above shows the powertrain unit removed from one of the longtail Gulf GTRs - this is probably the best shot to show the placement of the transmission. It should be noted though, that the longtail GTRs didn't use the same transmission as the standard F1s and shorttail GTRs, but instead featured a sequential version of the design developed by Xtrac.
>8^)
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