There is an interesting short period piece on Youtube titled " Vintage Rally Racing 1974 " which includes two works orange cars being demonstrated to journalists. If anyone has found any other period rally films please list below.
Midnattssolsrallyt 2018 - Anders Knutsson, Saab V4 - Grymt motorljud! Copy and paste into Youtube
My favorite bit is at 4 mins 40 into the film, now that's how a V4 should be driven on gravel!!! This car must have some serious horse power!! I'd guess around the 165-170 mark.