Cessna 421 pilot reported a failure of aircraft communication systems after takeoff resulted in entering class D airspace without clearance.

Narrative

Company; had just acquired and purchased Aircraft X; a Cessna 421B on Day 0 of which it immediately went into Annual inspection with FBO X at ZZZ. Annual inspection was completed on Day 1 and the aircraft was flown from ZZZ - ZZZ1 - ZZZ2 on Day 24 where it was to have major avionics replacements as several flight systems were problematic and work was to be performed by FBO Y. During this time; the Primary Flight instruments were replaced with an Aspen EFD1000; COM 1 was replaced with a Garmin 430W GPS; the transponder was replaced with a Lynx L3 NGT-9000; the engine monitoring system with a JPI EDM 760; 2 Comm Lemo jacks installed; an instrument inverter replacement; troubleshooting of the auto-pilot system; and 4 USB connections. Six weeks later; the aircraft was completed and a short flight from ZZZ2 to ZZZ5 was planned to place the aircraft at it's permanent location. Shortly after takeoff aproximately 10 minutes into flight while establishing cruise; the aircraft started to receive major static and indecipherable communications through COMM 1 and COMM 2. Pilot attempted to troubleshoot and clean up squelch to no avail. Pilot then attempted to reboot avionics and radios. During this time the Garmin 430W would not reboot; loss of auto-pilot and yaw-dampener would not return; and only COMM 2 was available and full of static. L3 Transponder was still working and the PFD 1000. Without other means of navigational aid on board at the time; dead reckoning was used while continuing troubleshooting; and navigating in marginal conditions. The aircraft crossed over 2 sections of Class D airspace (ZZZ3) and (ZZZ4) which wasn't realized until days later after reviewing the flight. Upon further review the pilot should have SQUAWKED 7600 during communication loss however; the pilot reacted to operational risk management and wanted to ensure he could aviate and navigate to the destination of 56 nautical miles. The aircraft was successful in landing at ZZZ5. As a result of the incident Failure to Establish 2-way communication while crossing into a Class D airspace resulted.