My ex Aussie Sprint (VA178**) has the left and right indicators on the central dash cluster. That is coupled with the rectangular hazard switch on the dash.
Incidentally the original seats that came with the car have headrests but the drivers seat does NOT have the normal height adjustment mechanisms front and back my other ex UK cars have (the backrest adjusting handle is on the right confirming it was originally a drivers seat). Never actually noticed that difference before! I'm sure you could fabricate blocks which along with longer bolts could raise the seat so it is better to your liking.
It makes sense that that the twin repeater "pie chart" would be coupled with the oblong unlit hazard switch, if you use the unlit switch , you can still see the hazard lights are on as both repeaters light. With only a single repeater, you'd need a lit switch for hazards like the later one. It might be needful, to avoid circuit feedback, to delete the illumination wiring from the later switch to use it in conjunction with the early repeater dial.
The HRW switch on the series 1 cars was an afterthough illuminated job tacked on under the dash by the choke. Why they didn't keep this illiminated switch when they moved it to the dash, God only knows, I suppose it's neater to have all the lights in one place, but then the modified design puts the hazard warning light off on it's own instead, so swings and roundabouts. Very late cars had rear foglights fitted and the switch for those went where the series 1 HRW switch was originally located, plus ca change!
On the seat quandary, it's possible the guy who did all the competition mods replaced the adjustable height seat with a fixed one from a different model to comply with a compo rule. (A lot of compo rules forbid recliners and even reach adjustment) I tend to fit seats more suited to my odd shaped body, but when faced with a standard Sprint height adjustable seat, I run it on the lowest possible setting anyway. HOWEVER, if the foam and diaphragm is below par, even I run it higher! I'd check the condition of the cushion before writing the seat off!