Reminds me of my 1976 (P) 2500S. Mimosa yellow with Stag alloys as standard. Twin SU carbs instead of injection.
Overdrive made it very 'long of leg' although economy was still woeful at around 13 MPG, following a play with the Colourtune.
how the hell do you get it that low? Single SUs are excellent, but I've never seen a decent throttle linkage on a factory twin(or more) installation.
Colourtunes are pretty good but if using them on multiple carb engines, you want at least one per carb. I've a friend who tunes the quad Dellortos on his hotrod with eight of them, bought for pennies at various autojumbles.
The only way I could get it to run smoothly, and with immediate throttle response, was to have it running 'rich'
Set up to run properly on the Colourtune it would always gag and stutter as though it was starved of fuel and running too 'lean'
It's possible the carb needles and jets were worn and needed replacing. I was only 23 what did I know?

Lovely looking car though.