Nice looking Abarth replica you have there. I say 'replica' because Abarth (the Company) stopped making cars in 1971, when it was absorbed into the Fiat family. I see that you have an "Abarth style" instrument cluster---does it have LED bulbs in it or 'normal type' bulbs. I ask this because if you have an LED bulb in the ignition light, it WILL stay on. I have worn the 'T' shirt and seen the video on this problem----I have an Abarth-style instrument cluster in my car, and initially had a LED bulb in the ignition light---just could NOT get the ignition light to go out until I replaced the bulb with a 'normal' type.
Does your distributor have points or an electronic unit in it? I ask this because ALL the electronic units, irrespecive of cost, have a temperature "wilt" point---they do NOT like being exposed to over 100C, and the 'cooling' air coming across the engine, and over the distributor, will often exceed 100C after a 'spirited' run. If you have points, try to also keep the condenser away from the distributor---modern 'pattern' condensers will also wilt if continually exposed to high temperatures. Condensers which can be mounted away from the distributor, and up by the coil, are availabe.
75 bhp? I really would like to know how the engine builder got to that figure! What size is the engine in your "wee beastie"? Have fun with it, and USE it!