Survey pilot reported a near miss during cruise that required evasive action to avoid a collision.

Narrative

On Day 0; at XA40; I was operating a single pilot survey operation flight (with required Sensor Operator crew member on board) in a Cessna Caravan C208. Winds were from the north; flight conditions were mostly smooth; visibility was more than 6SM; some haze in the distance and temperature was 30C. After departing ZZZ to the north; we were approximately 25 miles north of the airport. Opportunities to check in with ZZZ Approach were almost nonexistent with the high volume of aircraft calls and controller instructions. As we were departing to the north-northwest; we leveled off at 2;500' MSL with the local altimeter setting. Continuing this track while proceeding to our survey area; and waiting for a space to check in and request VFR flight following; there was suddenly a high wing Light Sport Aircraft (Glasair GS2) less than 100 feet directly in front of us; approaching nearly head on; slightly left to right from the 1230 position with its front left cowl slightly angled towards us. When I saw this; I gently but firmly pushed the nose down and then pulled up to 'swoop' underneath and keep the tail out of the way of the opposing aircraft. I had no way of determining whether the aircraft was in a descent in the seconds over this occurred; or if they had even seen us. Immediate; purposeful and controlled movements prevented us from colliding; while also not upsetting the aircraft or inducing a zero G condition. The opposing aircraft was southeast bound at 2;500 MSL. A check of the historical data shows we were twenty five feet away from each other; most likely due to a difference in altimeter settings. After we passed each other; the pilot of the opposing aircraft keyed up approach and stated they had a high wing fly closely underneath them. I replied to approach with our call sign; and that we saw the other aircraft pass overhead. The controller took a minute to establish where the southeast bound aircraft was calling from; and when ATC got the appropriate information; he told the pilot that they were not in fact receiving services; so no traffic alerts were provided. The pilot replied they thought they had been cleared direct to the airport; with no traffic between them and the airport. The controller reiterated they were not providing them services. No other information was asked of either of us; and it appeared approach did not know which two aircraft were involved or where we were located. The opposing aircraft continued at 2;500'MSL to ZZZ. Our aircraft is equipped with ADS-B OUT; but no IN decoding equipment was available onboard at the time. When I was able to check in with approach; there was no mention of the close call; and the call I made after the event unfolded was not followed up. Approach confirmed the area we were going to be working in and handed us off to ZZZ Center right away where I received a squawk code and flight following from them. The rest of our day was uneventful.We were both at VFR altitudes that are not specifically regulated by the VFR West-Even; East-Odd rule of CFR 14 91.159. This incident does bring to light that below the stated 3;000'AGL there may be aircraft at any altitude in any direction.The pilot display screen we use to give us information to fly survey lines sits above the glare shield; and obscures a portion of the right center windscreen. Moving your head around enables the pilot to see behind this blind spot; but it's a blind spot nonetheless. Coupled with a target not moving sideways; but 'stationary' as it was coming towards us; and this created a perfect combination to miss any traffic in the haze until it was right in front of us.Removing the display and equipping it later rather than earlier; and installing equipment that can provide ADS-B traffic data IN will be implemented in order to improve 'see and avoid' operations while VFR.